Bethesda games are buggy because they're gigantic and playtesting those monsters takes forever. The complexity of games is exponential, and considering that in games like FO3, Skyrim etc you can approach anything any way and just do crazy shit it can get really difficult. In mass effect you have an objective, you approach it, shoot some people, choose a dialogue and you're done. The idea of the choices seems massive but in reality they're just a few pre set sequences. In mass effect you can't for example just randomly blast a quest giver away with some push ability, hell you can't even do anything to them except talk to them.
I love mass effect and games like it but shitting on bethesda for being buggy is pretty stupid. It's obviously they're trying (though they could do better) but comparing the tendency for their games to be buggy to anything else is flat out stupid. Not only that but they're one of the only companies left who haven't fully become heartless douchebags, note the great work on the construction kit, the free dlc they offered, the new way of doing mods (though still being allowed to do the old way), all the stuff they do for fans etc. I'm not saying they're the best no, but they're definitely better than most of the companies who wouldn't even dream of giving away something unless it is priced (and is still shitty).