Eh? ME2 had actual non-shooting missions, ME1 didn't. The diversity of gameplay was much higher in ME2, also than in ME3 sadly, wish there would've been more non-shooting missions.Exploration in ME1 is by far the best, even in main missions only, each environment was given time you were allowed to look around a bit, some places had no or little combat.
ME2 on wards you pretty much turn up as shit has already gone down, meaning one or two people to talk to and no substantial side tasks.