I completely agree with you on this one Wolfram01.
I only pre-order games that I'm absolutely sure to like, will eventually buy, and I might as well get the purchase over with early on (won't forget it's already come out) and might as well get a little something extra as well.
The last game I pre-ordered was Dragon Age 2. Just a couple days before, because I loved Dragon Age: Origins and knew I was going to buy it at some point, so why not beforehand. I also tried the demo, to see what the cries of dumbing down and changing too much were about. I've really enjoyed the game. Perhaps had most fun in gaming in a long time. Absolutely nothing to regret. Also, I've played for about 30 hours and I'm still about halfway through I guess, so it's not even short.
Portal 2, I've pre-ordered also. I hadn't played Portal before that, so getting it for the same discount price was awesome. I got my money's worth from the Portal alone and I've still get the whole Portal 2 to look forward to. And I'm convinced it will not disappoint.
The previous two, and only other games I've pre-ordered were: Fallout: New Vegas, and Civilization V.
I really enjoyed Fallout 3, and everything I read and saw about New Vegas was compelling. The environment especially. I've liked it far more that F3 even. A very good purchase.
I'm a huge fan of the Civilization series, playing Civ IV, and especially the final expansion: Beyond The Sword, to almost no end. I like everything they've changed: the hexagons feel like they should've been there all along. I've only tried it for about ten hours, for I've wanted to play other games lately, and do other stuff besides gaming and I know that Civ V will be a massive time sink. I really like the game, and the patches they've released afterwards, have fixed the slight problems the final release initially had.