I try my best. Usually the games I have that are unfinished are that way because of lots of time spent at work/school.

I am surprised at how often I don't finish. I just play until I stop having fun and and then move on to something new or replay an old favorite.

I try to beat action/adventure games or just games with stories whereas I will only play a game like Need For Speed Hot Pursuit, Midnight Club, or any sports game until it stops being fun.

It does take me forever to beat games though as I don't play them all the time like when I was younger. I have a little cousin who's really into games now and beats shit like Pokemon 4 and 5 times and Final Fantasy 7 3 times. I know thats a bit extreme, but younger people just have more time to blow.

I also find that I have to be in a gaming mood to actually make some progress. I had beyond good and evil for two months. Played it off and on and then all of the sudden I got sucked in and played it until I beat it (over the span of about 3 days). RPG's get no love from me anymore (save for the excellent Knights of the Old Republic...even if it takes me a year to beat.)

If the game is worth finishing, then I finish it. If not, then I usually never pick it up again.