I can't blame ME1 for having crappy combat/cover mechanics...I mean, before Gears of War came out there were no really decent TPS controls or mechanics...they were all pretty ****ty and ME1 was in development LONG before GoW1 came out.
Texture pop-in was an issue, and the framerate dipped a lot, but have you SEEN the ME1 graphics? They still look decent
today. I introduced my friend to the Mass effect universe in January and he instantly commented on how good the game looks considering how old it is, I remember being blown away when I first saw it, it was easily the best looking game i'd seen and stayed that way for a while.
The inventory system and HUD was a mess, that's patently true (read
this for all the gory details, a pretty interesting read)
A lot of the side quest's had copy/pasted/slightly altered "Dungeons" (or whatever the sci-fi version is), that is also true.
On the whole though, I agree, ME3 is my favourite in the franchise so far for gameplay and up until the ending the character interaction was amazing too. But ME1 is only a nose behind, despite its flaws because of its plot (for me) - The plot in ME1, with Saren and the discovery of the Reapers, is the best in the series.
And, in ME1 they really nailed the end. I mean I ****ing love the end of ME1, It's a brilliant climax, a REAL stand off with your nemesis that has hunted and hindered you throughout the game (both an intellectual battle and a physical one), a gigantic battle with an unbelievable evil raging on outside, getting to make quick decisions that will affect the galaxy...and of course being buried under rubble, looking to have sacrificed yourself for the greater good...until...OH SHI- SHEPARD'S ALIVE! And he's like "What? You were worried? Please; I'm commander ****ing Shepard."
Fists are pumped, and I am left feeling an immense sense of satisfaction and glory. ME2 didn't have that nearly as much, and ME3 should have had that in spades but failed even to top ME2...or even be workable.