In the United States:

Legacy Carrier Seat Pitch
Domestic First: 36" to 38" avg, 34" on some NWA planes. (just keep this number and that its first class in mind when I get to seat pitch in Low Cost Carriers)
Domestic Coach: 30" to 32", avg 31"

Low Cost Carrier Seat Pitch
jetBlue: 32" to 34" (effective March 1: 34" to 36" on the A320, 32" to 33" on the E190)
Southwest: 33"
Note: soon on jetBlue you will get about the same amount of legroom as the average domestic first class cabin on legacy carriers but with out having to pay a premium (since jetBlue did state they will not charge more for the 36" seat pitch seats which is 1/2 the cabin)

LCC Service Offering More:
jetBlue and Frontier offers live satalite TV in flight, so does WestJet in Canada and Virgin Blue in Australia, all discount carriers.
Virgin America, once approve to fly by the DOT, will offer the most technologically advance inflight entertainment system ever.
jetBlue and AirTarn offers live XM radio in flight
of the legacy carriers, only Delta offers this IFE service, but its only on select aircraft on select routes.
jetBlue offers amenity kits that contains eye mask, lip blam, and other spa product on "Shut Eye" flights.

Free Service:
Most legacy carriers are charging for snacks and bottled water on domestic flights. Example: American Airline and their expensive bottled water.
jetBlue and Southwest still offer drinks and snacks for free. Infact, jetBlue offers like 2 or 3 selections on short hops and more than 6 or 7 selections on longer flights, bottled water are still free (same brand as the one American sell), and jetBlue even set up a self service snack bar on longer flights.

Windowsades, all the lcc carriers I've been on have window shades.

Cabin Comfort:
Not mentioned but here I go.
Leather Seats on jetBlue and Virgin America! Way better than the nasty coach seats on the legacy carriers.

Basically what am I getting at in the US, the legacy carriers seems to be offering less frills than their LCC counterparts.