In the past week I bought, played and finished Mass Effect 2 (on PC) and I want to strongly recommend this game. It's really great. I generally like RPG games. I also played and finished first version of Mass Effect and liked it.
Version 2 is much better though. Graphics is better, more detailed. They've removed all the annoying things like long elevator travels or driving "Mako" on the planet surfaces. They've introduced some nice minigames instead - gathering resources from the planets (quite boring but I liked it), hacking electronic circuits and hacking code (which are great ideas). As a main gameplay, they've taken all what's best in modern RPGs (like lots of talking, hard moral choices, nonlinear story, personal history and problems of characters) and shooters (like cover system, aiming, boss fights). Game is quite long (it took me 9 days to finish it), but as for RPG it's an adventage.
As a summary, I strongly recommend Mass Effect 2 to anyone who likes RPGs and/or shooters. I can't remember when I played any game so passionately since The Witcher, and I played dozens of great of games since then. I'm glad I'm not the only one who thinks Mass Effect 2 is great - professional reviews and sales indicate it's generally very successful.