I'll play.

I prefer LGA for the cheapest cabs to where I usually go (Brooklyn; UES). JFK has a flat-rate for cabs to Manhattan ($45 now?); it's metered the other way, so depending on the time of day (which we don't know), can be either favorable or not so. I avoid EWR, since I'm usually going from Brooklyn, and car service can be over $100; others can weigh in on what cab fare is like to various parts of Manhattan.

Re the train from EWR. As other people have mentioned, it depends significantly on when your flight arrives. You have to take a monorail to the EWR station, which connects with northeast corridor trains into NYC. Not all NJ Transit trains stop at the EWR station (and, as has been mentioned above, you're not walking there). At off-peak hours, you can wait 40 minutes or more. During peak times, the train will be full. Amtrak is quite a bit more, but not really any faster. Sometimes it's difficult getting an early enough train if you're taking a 6 am flight (maybe schedules have improved-- it's been a while since I've done that).

Finally, you'll arrive at New York Penn Station (always a joy). Whoo, yet another chance to schlep luggage through crowds! It's especially fun around 5:30 pm on a Friday night! From there you can take the subway, or a cab, unless you're unlucky enough to be staying around Penn Station.

If you're traveling alone, the train (plus a cab or subway once in NYC) from EWR will be the cheapest (and there's also the bus). If you are two or more, a cab from LGA or even JFK isn't much more (or even less overall) and is hassle.

Obviously, I dislike EWR, but with more specific info on where you would be staying, someone else might be able to tell if EWR isn't as irritating as I have made it out to be.