Christmas Ape wrote...
Every alien is more or less humanoid (with a couple of exceptions)
At least two exceptions, possibly four - we've yet to see the raloi and volus may just use humanoid suits for convenience when interacting with humanoid species.
speaks english
Bzzzzzt! Sadly, the codex entry on translation only comes with BDtS
have near-human cultures and habits
...haven't read much on the salarians, I take it? And other than that, I have a hard time coming up with cultural traits that are both never expressed on Earth and not just weird for the sake of weird.
and breathe oxygen
Err, not all of them.
I never argued it wasn't all perfectly logical within the confines of the ME universe, only that it all flies in the face of real-world logic/studies/ect, since people think they should be applied to some aspects of the game and not others. I actually think the idea the Protheans and/or Reapers impacted the evolutionary paths of most or all of the races is an interresting and heavily implied one - it'd explain the simularities. Well some of them.
Apologies for not having read every codex in the game, I don't know everything about ME, I admit.

Just my 2 copper. Those were just examples, I'm sure there are many better ones. Those just came to mind, and they're hardly the oddest things in the game *cough*Asari mating*cough*. All of this said, I love ME I wouldn't change a thing. You may have inspired me to read some more in-game codexes though.