>>91458913ME1 has the jankiest combat but the most coherent story and best writing. It's also the only one I would still call an RPG, 2 and 3 are just action games with light RPG elements.
ME2 has good companion quests but the main plot is full of holes and it's kind of a filler game. This is where they really started dumbing down the RPG mechanics.
I never played ME3 after it was patched and with the DLCs because I was so disappointed with the game after completing it immediately after release. The fact that they put an important character behind DLC was fucking insane, combined with the ending being a total mess made me hate the series for a couple of series, but I look upon it more fondly now. Probably because we barely get AAA RPGs these days.