Basically 2DF FreePlay is a matchmaking frontend for the nFBA emulator. All you need to do is to install the required program, grab some roms, make an account and off you go. It currently supports a lot more games than GGPO, although the client doesn't have as many features as GGPO does yet. GGPO however does have a major update coming at some point. Games supported are:
Super Street Fighter II Turbo
The King of Fighters '98 - the slugfest
The King of Fighters 2002 - challenge to ultimate battle
The Last Blade 2
Street Fighter Alpha 2
Street Fighter Alpha 3
Vampire Savior - the lord of vampire
Vampire Savior 2 - the lord of vampire
X-Men vs Street Fighter
World Heroes Perfect
Waku Waku 7
Super Puzzle Fighter II Turbo
Samurai Shodown V Special
Real Bout Fatal Fury Special
Night Warriors - darkstalkers' revenge
Marvel vs Capcom - clash of super heroes
Garou - mark of the wolves
Real Bout Fatal Fury 2 - the newcomers
Karnov's Revenge
Samurai Shodown IV - Amakusa's revenge
The King of Fighters 2000
Street Fighter II' - hyper fighting
X-Men - children of the atom
Street Fighter II' - champion edition
Ninja Master's haoh ninpo cho
Fatal Fury Special
Breakers Revenge
Twinklestar Sprites
Marvel Super Heroes
Street Fighter 3: Third Strike
JoJo's Bizarre Adventure
http://www.damdai.com/2df/freeplay/I played Last Blade 2 with a friend in Europe and had almost no lag. Has a few non fighting games too. Try it.