I used to feel this way about single player games. I used to feel that the only way to get my money's worth out of a game was to make sure that game lasted as long as humanly possible. One of the only reason I played JRPG's was to know that that 50 bucks was going to be worth at least 3 months of gaming. However, I've advanced from that time to really appreciate quality over quantity, and I've come to appreciate games that are quite the right length, including Gears of War (the first one), Portal and Braid. What gets me about a game now is how well they've put it together, and when the game lasts just long enough to be satisfying but not drag on, it feels good to me. In fact, I've had trouble finishing up the MGS series because I feel like they filled it with a bit too much filler. I'm still on the third one and haven't played it in a looooong time because of that change in my gaming habits.
If you want a game that'll last forever though, I still say: Look into games with endless replay value like Pac Man, Intelligent Qube, Ikaruga, or (the more recent games of) Grand Theft Auto. All of these games have endless reasons to replay through them, be it the goal of score or the wide world or just pure difficulty. Honestly, I think the biggest factor here is becoming more mature as a gamer and learning just what kind of quality you're getting out of the game. Once you can recognize the attention paid by the creators to certain things, you'll be able to appreciate the smaller things even more, and you'll get more enjoyment out of the time spent, even if the time is somewhat less.
