Maybe I just got lucky, but I did not encounter any significant gamebreaking issues involving frame rate or tearing in Mass Effect 1.
In regards to your game mechanics issues, I am right there with you when it comes to a hatred of the vehicle sections. The aggravation of the controls combined with the poor physics and massive worlds requiring tedious driving with no action were frustrating to say the least. Bioware "fixed" this issue by sidesteping it and just removing it in the second game, a poor move imo since the game loses combat variety even though the vehicle combat was awful.
The issues involving the story you mentioned did not seem to effect me. Sure, the primary planets can mostly be visited in no particular order but your choices did have some effects on the characters ... Liara's rescue, for example, changes based upon the order you do the missions with her reaction to you being altered.
I understand where you are coming from in regards to big games getting a "free pass." However, I believe that the Mass Effect series, despite its issues, earns its praise. Even though Mass Effect 1 was a new IP you could argue that reviewers were just looking for any excuse to love it since it came from Bioware (which we all fell in love with after old republic games). By looking at another similiar example of Too Human (new ip, exclusive to 360, from respected Silicon Knights developer) we can see that reviewers had little trouble panning it for its many flaws.(6-6.5 scores or so which are well below Mass Effect)
