My vote looks like this;
1) 360 - The head start was HUGE. The library is there. Xbox Live got pimped, and it was already kickass as it was. Once the bigger HDDs come out and they start offering HD Movie downloads, it's all over.
2) DS - Cheap, it's got a growing catalog, and people like having a portable. I was dead set against the idea of a new Game Boy when this came out, and now I'm starting to warm up to the idea of owning one. Man, do I want Final Fantasy III and the new Super Mario Bros.
3) Wii - Still the best first-party games in the battle. Cheaper price point, with the aforementioned gimmick that brings in both gamers and non-gamers alike. I'll own one of these, once the library deepens a little bit.
4) PS3 - Cost-prohibitive, impossible to find, and there's nothing out for it that I'm even remotely interested in. But hey, it ships with Ricky Bobby!
5) PSP - Has already failed. If it weren't for Rockstar pushing out a new installment of Vice City, these things would almost be on the clearance rack for the holidays.