It managed to make winning feel like losing in a spectacular way.
I mostly enjoyed the majority of the game since I set my expectations low as I somehow had a feeling Bioware would drop the ball on this one... I also avoided spoilers and anything related to the game before getting it, so i would come fresh to it. Then I was pleasantly surprised to see the game was playable and entertaining almost to the end during my first playthrough with my ME1/ME2 male standard-faced paragon Shepard, minor things i didn't like much like the new quest and exploration system and a few cheap melodramatic moments (not saying they were all cheap) the gay stuff didn't bother me but wasn't well done either, kinda shallow, but not offensive, i found the fact that refusing the homosexual advances gave you renegade points hilarious, my guy had Liara on 1 and Miranda on 2, i chose Liara again for 3 (although this apparently ended up killing Miranda)
After the totally disappointing and illogical ending, I restarted with my ME1/ME2 custom-faced renegade femshep trying to get a better ending and then hit the first hurdle: A bug that doesn't let you import your customized Shepard Face from ME1 and gives you with an error. There's a convoluted workaround on Bioware forums that brings the appearance partially through something called the face code but it doesn't work 100% and you end up having to touch it up with 3's face generator and it ends up looking different, no matter how hard you try, since there's less customization, I think the problem is they changed the custom "face system", probably due to multiplayer, and all faces have suffered for it, in fact the faces were pretty much the same from ME1 to ME2, actually better, but in ME3 they don't look so well, for example: Joker's new face is awful, my first impression was: "is that Joker? what happened to him? looks psychotic"
Long story short, I had to settle for a Female Shepard that doesn't quite look like mine, which is actually the one i spent most time with and go 100% completion because i love Jennifer Hale's renegade lines... but then... the lines are not that great in the third installment, the renegade character's inconsistent due mostly to annoying "autodialog" or few conversation options, especially during the moments involving "The Kid" kinda like what happened in infamous 2 were there are not enough lines to flesh out the badass character and you end with touchy-feely, loving and caring renegade Shepard... so she doesn't sound like my Shepard either.
The Combat system is pretty much ME2's with some tweaks here and there... so it's okay i guess, didn't like that there's not much variety in the enemy department and you're basically gonna be fighting the same ones through the whole game only increasing in numbers and waves to raise difficulty (no more awesome and unique boss fights) just more enemies for example brutes are though to beat... then the boss for the area is two or three simultaneous brutes, same for banshees, atlas robots, etc.
All in all ME3 is good but not great... and somehow makes me feel sad and like I'm done with the series.