A game's greatness means nothing for its "canon" either though, of course... I love X-Wing: Alliance, it's a fantastic (if unfinished) story that fits flawless into the story of Star Wars but it's not canon...
The things in BF that I always disliked and made me look "down" on it as far as "canon" goes are the things like armor not changing for troopers and things, the way armor is different for a heavy trooper but he isn't the trooper appropriate to that legion, etc... Just weird stuff.
I dig some stuff about the games, I can see things loosely fitting into continuity, but the way the game plays kills a lot of it. THe story is weak too, the game isn't story-centric as much as it's just a "plug through this map, then plug through that one" game format. It's not like, say, X-Wing: Alliance where your earlier mission builds into your next, cut-scenes carry the story along further, training plays a factor, etc., etc., etc...
BFI or II are both ok for what they are but their various "elements" are things I pick and choose how they fit into the SW universe... Like I dig the Tat. Skiff being used as an infantry vehicle, like it's something common on planets around the galaxy, but there are things like the armor issues and whatnot that retard the game and its believabiliyt overall whereas other games like Dark Forces fit into the SW universe flawlessly really.