I think MMO gaming has something to do with draining the fun out of regular games. I used to play regular games like crazy until I got way into City of Heroes and it gradually eroded my interest in regular console gaming due to the sheer amount of my free time that it consumed. Then once CoH got stale (and since died) my interest in other games hasn't come back. It doesn't help that most of my gaming was dominated by the PC and I don't often get the hot new properties like Gears, Halo, etc.
Money is definitely a factor also. I just can't afford to drop $60 on a new game, but Steam sales provide massive discounts that make it possible for me to buy and play games without having to worry about spending my meager disposable income.
I tend to find one or two games and focus on them intensely as opposed to playing everything like I used to do. Right now my main crutches are Skyrim and Borderlands 2. I tend to play BF3 for short spurts now and then also, but that's about it.
I think once the next console generation gets rolling I may get engaged again. I'm 28, btw.
Asus Sabertooth Z77 | Intel Core i5-3570k | Cooler Master Hyper 212+ | 16GB Corsair Vengeance 1600 | Evga GTX 670 FTW | Crucial M4 128GB SSD