Personally, I liked the first Mass Effect more than the sequels, despite the technical limitations. I thought the story and the characters were more interesting, and the RPG elements were a lot stronger. All that seemed watered down in the sequels, with an emphasis on shooter mechanics. The first game also had a sense of wonder that was missing in the others, in part because it was the original, a new creation, whereas the sequels were ... well, sequels. I played the first game three times (very rare for me). One of my favorites.
me1 had that feeling because it had a story and actual exploration. me2 was a straight-road of babysitting missions; and they replaced exploration with that probe minigame wtf (yes i'm still mad at the changes)