I'm not sure. Maybe not, or at least not at first, anyway. I was a SEGA fan looking for a new home, and NO WAY was Nintendo going to be an option, so it was either Xbox or Playstation for me. My parents got me a PS2 for Christmas one year, and I got a few games for it (including the original Killzone), but I never really dove into it. I wasn't a big fan of the controller, and there weren't any PS2 exclusives that had really grabbed hold of me. It's possible I might have settled on the PS2 had Halo not come along, but it's hard to say.
I got into Halo and Xbox when my friends all started playing; I wound up getting an Xbox around the time Halo 2 came out, so I could join in on the fun without having to use other peoples' consoles. Without Halo, it's hard to say if I would have gravitated towards Xbox so soon. To be fair, though, it wasn't just Halo that got me hooked on Xbox. The controller (namely the S controller) was easily my favorite controller of that generation; its button labeling and thumbstick placement made for an easy transition from my SEGA Dreamcast. Fable was also important; that game caught my imagination, and I've been a fan of the series ever since.
The 360 only further solidified my leaning toward Xbox. Once again, all my friends (who played videogames) played on Xbox, and I had great times playing a variety of games, including Halo, Fable, and Mass Effect 1+2 (ME, which was Xbox exclusive at the time, was the main reason I first got my own 360), as well as a ton of great XBLA titles.
