I had this feeling for a few years around 1999 to late 2003, basically due to being semi-addicted to an online game. However I then made a conscious decision to put more effort in to starting SP games and giving them more than just 15mins. The problem is that I'd got so used to the 'quick fix' of familiar multiplayer that anything slightly out of the ordinary that wasn't complete pick-up-and-play didn't get much of a look in. If it didn't hook me straight away, it was discarded.
There are good and bad points to my new policy. I keep a little record of the games I've completed (as in, beaten the main story mode, not 100% completion) and it's now reached about 100 titles. Over the past 6 years I've given a chance to and been enthralled by games like Deus Ex, KOTOR, CoD, Far Cry etc some of which I had overlooked when released. But equally I've grinded through some fairly generic games that really weren't worth the effort - stuff like Pariah, Area 51, MoH: Airborne, Mashed, Rainbox 6 Lockdown etc. These are not exactly legendary games and will not live long in the memory.
I don't fall into the same trap as Uriel though, it is very rare I restart a game without finishing it. I horde my savegames and have plenty that are well over 5 years old waiting for me to go back to them (case in point being GTA3 which I went back to at the start of the year after a 6.5 year break, I was near the end of the second island).