As a 360 owner myself, I have to say that the time gap between the 360 release and the release of the other systems is quite significant. I think it needs a little more time before we can clearly declare the 360 as the top winner. Volume of games doesn't necessarily mean a win, because often when a system has a lot of games, a good portion of them are cheap bad games or franchise milkers. Games do matter, but it's the third party game makers that matters most. The PS2 snagged Square, snagged Capcom (for the most part) and other very good third parties. That was what made it's success, not it's cheap dev kits which anyone who wanted to make a name could get. Quality games are what attracts gamers. However, an overly expensive dev kit can repel even the best and richest game studios.
However unless Nintendo manages to convince third parties to make good games for the Wii, the 360 most likely does have the upper hand. It was the first out, and it has an inexpensive dev kit. However it does seem the novelty of the Wii does attract some gamers, so it's really a toss up to see which climbs out on top, 360 or Wii.