ME2 was fun, but not as good as ME here's why I think so:
1 - Leveling, 5 abilities and a weird points system, nuff said.
2 - Planet mining. The Mako was fun, the controls werem't as bad as people said.
3 - Story, Mass Effect brought you into a galaxy threatened by an immediate enemy, each mission mattered, and you were a spectre, which was cool. You made derisions and Mass Effect 2 was just preparation, more preparation, and then you fight some aliens. Oh, and you're working for Cerberus, which sucks.
4 - Characters, Liara was basically a nerd, Ashley was a soldier to the core who was xenophobic, Garrus was a renegade cop who wouldn't play by the rules, Kaiden was a bit lacking in depth, but he was still cool, Tali was curious bubbly genius. In ME2, Liara is a ***** all of a sudden, Ashley stays the same, Garrus never talks, Kaiden suddenly acts like a woman and then you've got a bunch of crappy characters(Aside from Grunt, Kasumi, Zaeed and Jacob).
5 - Paragon means illogical in many parts of the game, any favour for the genophage is somehow renegade? "Don't hide behind statistics!" has to be the stupidest line I've ever heard in a game. And not destroying the human reaper makes sense, it should be studied, and the collector base has valuable tech that could be used against the collectors.
6 - I just preferred the soundtrack in Mass Effect.
Once they remove planet mining and make the levelling more like the first game ME3 will be great. Also, more characters like Zaeed, he's awesome.