Being french I played all three ME with french voices, but I'm also accustomed to the original english voices because most of the stuff I find about ME ( youtube, interviews of the VAs, this forum wich is to me far more interesting in english than in french ) is in english.
I feel quite "splited" between the two versions, I really like most of the french voices but a lot of things get lost in the translation, the better example is Tali, who has absolutely no accent in french, so when I heared her original voice I was astonished by the change. Drells also all have pretty much the same voice. And Chakwas seem stoned all the time, but I find it is quite the same in english.
I guess the feeling depend greatly for each language, simply because the translation and voice work can be done with great dedication for some and poorly for other.
In french for example as I said I think most of the voices are greatly done, there is some errors sometimes ( for example the asari commander in the Destiny ascension at the end of ME1 talks with a male salarian voice, pretty weird ), but overall it is good.
The problem now is that I would like to play in english, the change should'nt be that difficult for most of the characters, but I'm kind of annoyed by the fact that in my head Shepard's french VA = My custom shepard, and Meer voice = default shep. That's the biggest problem to me
And Jaavik does sounds badass in french 8)