For me the redeeming strength of the Mass Effect franchise is the character interaction, and this was easily strongest in Mass Effect 2, so it's my favourite. Mass Effect 3 was also good in this regard, but the ending, limited squad, and removal of all the most interesting characters from ME2 make it slightly inferior in my book.
Regarding the lack of "exploration" in ME2 and ME3, I'd rather stab my eyes with a rusty fork than have to drive that Mako to the mining facility or big room again (of course followed by terrible, repetitive combat within said room). I don't care if they changed the hue on some of the skyboxes, you were essentially doing the same thing over, and over, and over again, and that thing wasn't even fun (especially on the planets where they turned up the verticality slider, rendering the mako basically inoperable).