@zinc, I think you'd have a hard time justifying that ME2 is a "better" RPG. It's pretty much the same. It's the KOTOR formula all over again. Good, Neutral, Bad, be good or bad enough and you get the special Really Good or Really Bad options. That's Mass Effect RPG 1-3. In terms of character progression there is a hell of a lot more variety in ME3 than ME2.
I'd argue that ME3 has better interaction with squadmates and crew. Certainly you can go to whatever isolated part of the ship each individual has decided to park themselves in and they will spew out some story at you now and then, but that's it. In ME3 you have that, but at the same time when you wander around the ship characters actually acknowledge each others existence and interact. That's more depth than ME2 imo.
As for "more worlds to explore", yeah, you can go "free roam" around Omega, Illium and Tuchanka, there's practically nothing in them thanks to the shocking lack of side-quest content in ME2. The Citadel might be the only place you can properly wander around in ME3, but shit actually happens there. You can pick up missions there throughout the game, it's somewhere worth stopping by regularly.
As for fun, planet scanning sucked the fun right out of ME2. Whoever designed that should have been fired.
Aside from all that, ME2 felt like a game that had half its content scraped out to be sold as DLC. Barely any side missions outside of recruitment and each characters "loyalty" mission, compared to ME1 and 3 almost no variety in weapons or armour unless you cough up for dlc.
The story also feels like filler to me. The entire Collectors arc feels like stalling while they tried to figure out how to actually make a game about a Reaper invasion. It's like a piece of side DLC that somebody decided to try and stretch out into a full game. That feeling is further enhanced when you actually play ME3 and it's almost as if ME2 never happened. The events of ME2 are referred to only in extremely vague terms and in passing, the events which lead to Shepard leaving Cerberus are not playable, none of the characters introduced in ME2 make a return as playable characters unless they came from ME1. There are cameo appearances in a sort of "keeping up appearances" vein, but none of them are particularly central to the plot. Indeed if you start a fresh ME3 game the only ME2 characters Bioware decided survive the suicide mission are Miranda, Jacob and Mordin and references to any of those working with Shepard in Cerberus are kept to a bare minimum.
All in all I thought ME2 was a mediocre 3rd person cover shooter with a disappointing story that failed to live up to the promise the events of ME1 should have led to.