If ME2 carried the same quality story and breadth of RPG-style customisations (albeit cleaned up with better menus) as ME1, it would have be an awesome title with vastly improved gameplay. As noted earlier, ME1 had a superior story, but the menus were horrible and the combat was almost an afterthought. As it stood, ME2 was an excellent title with a dodgy plot and limited customisation but with fun, vastly improved combat.
Most of what I have seen of ME3 so far has focussed on the combat mechanics- the easiest things to show off- which look to have been improved yet again, but until menus and choices emerge, it is unfair to make a call about the game at large. I refused to read the spoiler dump a few months ago, but fully expect a series of major battles, a hunt for horcrux... errr pieces of deus ex machina, sprinkled with noble deaths of much loved characters and expressions of undying-love-until-I-get-on-my-next-ship-and-check-out-my-hot-first-mate to my beloved Liara/Ashley etc. It's the climax to a space opera that has been two games in the telling, so I don't expect too much by way of twists, more an opportunity to see it to bring the threads together.
tl/dr: if it's ME2 mk2, I'm ok with that. If it's ME1 with an improved ME2 combat system, better customization and a coherent overarching plot= killer.