The reason I got Xbox Live (seriously!)
Virtua Fighter 5 finally brought this precision-tuned fighting series online. Despite Sega's earlier claims that a game this precise, where a single animation frame means the difference between a hit and a miss, wouldn't work online because of lag issues, it is one of the best online time-wasters out there.
All of the classic characters from Virtua Fighter return. The two additions to this edition are El Blaze, a luchadore (lucha libre seems to have been the next hot thing for fighting games a year ago), and Eileen, a young practitioner of Monkey Kung Fu. The engine is as precise as ever, even online. I've seen minimal lag on VF5 compared to DOA4 or Halo 3, which are admittedly both more popular. Matches in VF5 become tense games of cat-and-mouse, where you must decide when to let down your guard to unleash your attack. Also, you must be aware of possible enemy counters, as VF5 still has the throw escapes and counters (thankfully not as easily exploited as in DOA4) that the series is known for.
VF5 has some of the most beautiful graphics of any video game ever made. The coloring and lighting is top notch, and the details to the characters, their costumes, and animation are impeccable. Why can't adventure games and RPGS look this good? The backgrounds are nearly photorealistic, although falling in the water still causes the same cheap effects seem on back on the PS2.
The only complaint I have to the online fighting is that its interface is fairly basic, not much more advanced than Gametap. There is no spectator mode, which leads to minimal conversation and socialization between players. There is strictly 1-to-1 fighting.
That said, playing online across the globe using this fantastic fighting engine pretty much makes up for everything else. I've burned up more XBL time on this game than any other. I play Soulcalibur IV and MK vs DC when I want to socialize. VF5, in my mind, is more like fighting game chess. Its depth is not for everyone, but if you're willing to learn the system, it's incredibly rewarding.