Personally, I'm getting all three eventually because I'm a multiconsole gamer, but if I was to pick a console I'd get first, or which one appeals to me the most it'd be the Xbox 360. With an 360 I don't think I'd need a Wii or PS3 for a long while.
My reasons:
1. The most varied console, that has big guns across practically every genre.
2. Xbox Live and emphasis on online content.
3. Xbox Live Arcade
4. Xbox Live Marketplace and downloadable new content
5. Most of the software are new IP's, and interesting ones at that.
6. Good balance between Japanese and Western support.
Operation Darkness
Culdcept Saga
Eternal Sanata aka Trusty Bell

Lost Odyssey
Blue Dragon
Mass Effect
AWWWWWWWWWWWWWWWWWWWWWWWWWWW YEAH. Watch this Dead Rising
Lost Planet
Lumines Live
Gears of War
Saints Row
Dead or Alive Xtreme 2
Dead or Alive 4
Bioshock


...
And many more.Not to mention downloadable content for Guitar Hero 2 (which also includes xbox live play and co-op), GTAIV on the same day as PS3 (AND with 2 add on packs exclusive for 360), Assasin's Creed, and other mutliconsole games. Once X360 has more Xbox games on backwards compatibility list, we'll have even more to play, including tons of arcade style games, and online fighters. Street Fighter Anniversary Collection please.
I'm honestly shocked how well MS is doing with this new console in terms of games and support. I envisioned me being way more excited for ps3 than 360, especially because some of my favorite franchises will reappear on ps3, but it seems I want more than a return of my favorite series'.