I agree, to an extent. Morrowind does have some fairly memorable quests, I haven't played it in a long time but I distinctively remember some really interesting quests you could do for the Daedric gods. And some random cool side quests, those beginning ones in Seyda Neen are really memorable, like stealing the dudes ring.
But then you have such memorable quests in Baldur's Gate 2 like the one where you have to track down a serial killer skinning people, and it spans over several different side quests, epic. Or the cult of the eyeless quest, or the shadow dragon. Yeah, fuck, some really memorable shit there. The expansion had some awesome stuff too, not as good though.
Morrowind's advantage I suppose was always the open ended aspect, though there are some cool things to find, like the Orc who you find carrying "Umbra", or the line of quests where you work for this noble and eventually expose him as being crooked and get him arrested.
Icewind Dale (+expansion) and IWD 2 are the other great ones I don't think anyone has mentioned so far in this thread. Those dungeon crawls are very engrossing, just like actually sitting down in a basement and doing some hardcore D&Ding. I usually play epic Doom metal, like Candlemass.
Knights Of The Old Republic stands as being far more linear compared to BG and Morrowind, but probably the most non linear dialog and memorable story/characters/plot twists of any recent games.
On the actual topic of the thread, Mass Effect, well, I enjoyed it. But one thing that really irked me was the fact that you had little real choice in the progression of the game, and the "side quests" had absolutely no non-linearity, aside from dialog choices that still filtered you into the same situation. Bioware must have known this, I am just going to assume EA forced them to release it ahead of schedule, or the same reason they re-used textures (not enough space on the disc). Well, at least the combat was fun and you had a few choices with that.
And I'll stop my musings on RPGs, as I could go on for pages.