As far as series go?
I'd have to go with street fighter.
2 Turbo, Alpha 3 and 3rd Strike is pretty much untouchable.

But Tekken would be second.
TTT is the best of the series but could still do better with some balancing since having Ogre and a Mishima on your team is apparently an unwritten rule in tournaments. T4 is probably the worse of the series, but still somewhat worthy.

Anyways, as far as Tournament turnout/pot goes, Street Fighter and Tekken are always the highest. Both series has done a very good job in being user friendly and very deep at the same time.

Soul Calibur has personality, intensity, depth, tons of rewards, extensive single player, and beauty.

Games like Street Fighter, Tekken, Smash Bros., and Virtua Fighter have many of these features, but the Soul Calibur series has them all.

Tekken

Soul Calibur #1 (DC ver was sick)
Tekken Arcade Version (pressing buttons was fun)
Dragon Ball Z: Budokai Tenkaichi series (combos r sick)

ssb, with an emphasis on melee. its fast, very free form (different vertical aspect), great damage system, huge variety (compare jigglypuff and falcon, both high tier, and tell me if they really seem to belong in the same game), lots of frame precision, deep set of tech, and tons mind games.

all-in-all, if it had been balanced (how does bowser beat sheik?) then it would be the perfect fighting game to me.