Wait till the big price drop on the 360, when it's under 199$ for a premium then I say jump all over it. Microsoft hasn't given us much of a look into what they are bringing out next year (yes I realize Nintendo is in the same boat but he has a Wii already). I should have posted my impressions of having a 360 for a weekend. I was going to purchase one last year before Christmas but the hardware failure rates spooked me away. I got to sit down with the system for 48 hours about a month ago.
As a guy who has played mostly Nintendo and Sony systems, the games that were most fun for me were on the Arcade. The online play felt really over hyped, it works nicely but the people in the games really ruined the experience for me. I kept running into some real mean people, ie: I'd spawn and a team mate in crackdown would kill me instantly on purpose over and over again just because he could. I'd attempt to run away but he was so powered up I couldn't get too far. In gears I had the exact same problem. I'd pop out around a corner and if someone on the team wanted my spot, they'd kill me. So this kinda stuff was very frustrating.
I'm surprised you didn't include more DS games, there's quite a few big games coming out for it this year as well.
Prepare for termination! It is the only logical thing to do, for I am only loyal to Megatron.
