Some of the best games I've ever played were pretty short going by what people here are defining as short. Metal Gear Solid, Ico, Shadow of the Colossus, BioShock, etc. Quality>Quantity always.
I'd say that all of those games are pretty lengthy. Usually, a playthrough any of those games is well over ten hours long. In my opinion, an example of a short game is something like Heavenly Sword, which can be beaten in one sitting (It was Saturday morning and so I didn't have anything better to do, but it was still only four and a half hours). Adventure games like Ico or games like MGS always take weeks to play through unless you have a staggering amount of leisure time.
Anyway, I agree with most of the thoughts here about the length of Mass Effect and other games. It's fine by me! If I recall, most Bioware RPGs are 15-20 hours long anyway, so I wasn't expecting more than that.
Often, I don't beat games like Blue Dragon because, even though I love them, by the time I've gotten 40 hours in and am nearing the end of the game, something else has come out or I am sick of it and just want to move on. My clock read about 20 hours Mass Effect, and while I certainly didn't take my time, I didn't exactly rush through the game, either. I also died frequently because I was playing on Hard mode, and the game crashed about a zillion times (it turned out to be a cat hair on the disc). I'm sure that a few unrecorded hours were added to my playtime. It might not be the hundred-hour-long galaxy-spanning space opera that IGN's previews promised it would be, but I was more than satisfied with the game. It's one of my personal favorites.
Does anyone REALLY want every game to be like Assassin's Creed, filled with useless cutscenes that are acted and written badly and are about four times as long as they need to be and all you want to do is skip past some guards chattering that your target "gets veeeeeery focused in his work, making him an easy target . . . . . . . . . . . . ." and get back to jumping on rooftops? I'd definitely have concise storytelling like Mass Effect's rather than padded drivel. I love a long game that can keep my attention forever, particularly during holiday vacations and stuff, but I agree with everyone else here that a 25 hour game is more than long enough to still feel epic.
