What it really comes down to is my priorities in games. I favor playing Nintendo games over completely new experiences, so my default is buying a Nintendo system as that's the only one their games are on. There's something to be said for familiarity. This isn't an unknown concept for the games industry, new IP's are seen as serious risks by everyone: publishers are afraid to spend money to fund them, and consumers are either ignorant of them until word of mouth hits or they actively avoid them, trying to stay in their personal safe zones.
Since I'm already buying a system per generation, I tend to stick with only that one for the generation for a variety of reasons. In the past, I haven't been able to get other systems because my family is generally not well-to-do. Instead of blowing $350 on a new system to even be able to access the few games I want for it, I'd rather reinvest that money in the system I already have. That $350 equals about 6 Wii games, or Wiimotes, etc. There are only about 6 or 7 PS3 or 360 games I want to play. For me, the cost-benefit analysis doesn't really work out.
More often these days, another issue is time, as I've brought up more than a few times. It's the reason I didn't own a 3DS until a few weeks ago. I've bought five Wii games this year and haven't beaten any of them. One I haven't even booted up (Fragile), three others I've barely put an hour or two into (Xenoblade, S&P, and Rock Band 3), and the last I struggle to find time to play even when I want to (Monster Hunter), mostly because it requires around an hour time investment minimum each time I want to jump in. Gaming isn't the only type of content I'm into these days; TV shows, movies, comics, and ebooks are all vying for my time. I'm too young to have found a good balance for all of this, and I'm constantly seeking a good way to divvy up my time.
For these reasons, I'm single-console only. I almost bought a PS2 in the middle of this generation, but that was about the time HD remakes and digital ports started to hit so I decided to wait in a price reduction of the current HD twins. As for why I don't buy a PS2 for $50 and go wild with $3-10 games, I apply the same concept to systems I have access to without the upfront cost. There's a lot of Virtual Console classics I have yet to play.
I believe there's a distinction to be made between being a fan of a certain first-party and being a console warrior; I would classify myself in the former group. I like Nintendo games, so I buy Nintendo consoles first. I don't buy other systems, because that time and money could be invested in the system I already have since I'm already being satiated with more content than I'll ever get to play.
As for third party games, there are some like Monster Hunter I'm a really big fan of. The console itself has nothing to do with it. I was excited for Resident Evil 5 since I loved 4, and thought I would eventually play it someday. I've been paying attention to RE6 for that reason, too.
You can say I'm not a "real gamer" since I don't buy all the consoles and invest 100 hours a week into the medium, but for me right now, it's just a light hobby, and I know what kind of games I like. That's all.
