I don't know if I have a numerical ranking, but a good/middle/bad works for me.

Good:

DC: I live here, so I am a bit biased, and I live about four blocks from a Metro stop, so I can get just about anywhere I want or need to go quickly. Drawbacks are that it is not 24-hr, and price varies at rush hour and if you go outside of the city itself or close in suburbs. Oh, and, (underground) stations, not just trains, are heated/AirConned. Drawbacks are that if you don't live on a line it is not all that comprehensive, but then again it was designed to facilitate getting commuters in and out of the center city from the suburbs rather than point a to b downtown.

NY: Comprehensive (if in Manhattan--don't have any experience with elsewhere), one price, 24 hours. drawbacks are standing on a platform in August when the city and the station are sweltering.

Paris: goes just about everywhere, or so it seems, and relatively cheap (or so I remember)

Frankfurt, Munich and Berlin were all quite nice, though I didn't spend a lot of time on the trains, and in the case of Frankfurt and Munich only took the S-bahn commuter rail rather than the U-Bahn.

Middle:

London: Plus for being comprehensive, negative for being expensive. Also the conditions can be a bit hazardous.

Bangkok: the experience/price was great all around. The drawback is that it is only helpful if you are near a station and want to go somewhere the lines go--it has very limited coverage.

Poor:

Philadelphia: Though it was great for me when I lived there, the two crossing lines and a web of half underground trollys are perfect if you only want to go where they do. Otherwise it is a bit expensive and gritty.

-ww

My vote also goes for Moscow. Beautiful stations, excellent on-time performance, frequency of the trains, coverage. Its truly number 1, IMO.^

Chicago? I lived there for 2 years and...yes...it is pretty much garbage. However, the loud and squeaky El is as much a spart of the windy city as Wrigley Field and the lake! Here's my list:

1) NYC - good # of stops and good city-wide coverage, as well as great hours of operation give this one the top spot

2) London - can be a bit expenvise for some trips (try Westminster to Wimbledon for your pocketbook!)

3) Washington, D.C. (it's clean, the stations look cool, and there's carpet in the cars!)

4) Munich

5) Budapest (just feels cool)

6) Mumbai (ok, this is a joke)

6) Boston (kind of cool how they are really El's that run below ground, and you walk around at grade level)

Worst: 1) Chicago

2) Philly

3) Houston (One line....nice $2 billion experiment that got us the Super Bowl...once)

4) The DFW Airport train (The inter-terminal one...not the DART)

5) Rome (2 freakin lines....sucks!)

Never been to the Orient, but I must imagine that the Maglev to/from the Shanghai Airport ranks up there.....

Surprisingly, the line in Caracas is actually pretty nice.

How very odd. ;)

From best to worst, off the top of my head:

Montreal -- great coverage, easy to navigate
Hong Kong -- modern and efficient
Paris -- cheap, easy to figure out, lots of character
Munich -- clean, safe, cheap, simple
Washington DC -- the best US system
London -- best graphics ever, but it's a collapsing antique
Tokyo -- I'm sure it serves locals beautifully; I couldn't figure it out
Sydney -- good coverage but junky trains and we didn't feel safe at night
NYC -- no navaids, mysterious and overwhelming
Chicago -- erratic
Boston -- decrepit, esp. the 100+ year old Green Line

Atlanta: the good one price for the entire network, goes to the airport. The bad poor coverage, wait for train can be long even during peak times, some scarey stations

I like Montreals stations, but the subway cars just bounce around all over the place on those rubber wheel.

Torontos air conditioning is a godsend on those sweltering summer days.

London, extensive network, just really let down by serious overcrowding.

One of the nicest is Warsaw's new metro, still being built but the stations are smartly designed and the cars very big.

http://upload.wikimedia.org/wikipedi..._Wilsona_2.jpg
http://upload.wikimedia.org/wikipedi...Marymont04.JPG

Istanbul is good too with really cheap fares.

The most depressing subway system has to be the Glasgow U. Dark and dingy, its just old in a bad, smelly kind of way.

I could nominate several:

London, for its ability to keep going against so many odds, to be both wonderful and awful, full of history and its own, arcane little world.

Glasgow, for its toy train feel.

Paris, for the rabbit in dungarees, strapontins and ticket barriers that will have your arm off.

Budapest Foldalatti, if only for the little tune it plays at each station.

Prague, in the nation of poets for the lovely, polite "ukonc ete prosim vystup a nastup, dvere se zaviraji".

Oslo, for the Frognerseteren line magically turning from metro to mountain railway halfway through.

Tashkent, for the kitsch shrine of Kosmonavtlar.

New York, just so you can say "take the downtown A train to Brooklyn" and other such things.

Chicago, for letting you see in people's windows.

Berlin, for the reopened ghost stations, and odd Cold War history.

Brussels, for their determination to carpet metro trains, and make them reverse halfway through the journey.

Bucharest, for managing to remain safe despite the don't-sneeze-in-them fibreglass old trains, and stations that look fit to collapse (don't even try the escalators).

Jeez, I forgot how bloody small they are. I've always had to duck my head when stepping onboard and I'm not a tall guy

#1: Tokyo
Using the Tokyo Metro and connecting train lines, it is possible to reach just about every corner of the city. It can, however, be somewhat confusing if you aren't familiar with it and don't speak Japanese. Everything seems to be marked in English at least *somewhere*, but not always where you currently are looking. (I'm trying to explain this from the prespective of someone who would look at the English signs; I can read the Japanese ones, so don't pay as much attention to the English ones and therefore this may be somewhat off.)

The Worst: Chicago
Old, noisy trains. Infrequent service. Lately, every time I ride it they seem to have the train stop in the middle of my journey due to maintenance on the line somewhere. Only useful for a limited number of places.

Even Worse, But Not A Subway: Cleveland
Not really a subway (there are only two underground portions), but almost entirely useless. Trains only run every 15-30 minutes, and only go to a very limited number of even remotely useful places. Just about the only two stops that are worthwhile are the airport and Tower City Center. I think you could do away with the rest of the line and only the homeless would miss it. (This is my hometown...public transit in Cleveland is useless in general. The nearest bus to my house ran once an hour.)

Also adding an "enjoying the ride" vote for the Tokyo area network.
Those trains are generally very very clean. I also enjoy the announcements lots. Of course, my vote is for the ride during off-peak hours. I find riding during rush hours very traumatic.

Similarly for St Petersburg
- great artwork and decorations in all the stations
- very cheap
- never waited more than 2 minutes for a train, mostly under 30 seconds
- easy to understand system
- some stations a bit further apart than you'd expect

Worst public transportation in major US city:

Detroit.

Have lived here for years, and have not once set foot on a bus, and maybe twice on the elevated rail system in Detroit. Goes nowhere except within downtown.

Korea and Tokyo
 

Another one i Liked was Souel Korea. Easy to navigate and clean. Tokyo was great as the trains arrived on time and were modern and clean. Pusan Korea has a simple system that runs efficently.

For the size of the city Munich's U-Bahn is very impressive especially the way the S-Bahn is also integrated into the stations. I also like Berlin's, it somehow seems antiquated but works very well. Toronto's is great for me because I live right on the Yonge line but although the 2 main lines go a long way there really isn't enough coverage for a city this size.