Mass Effect is a difficult game for me to rate, simply because I can't make myself call it a great game because it had too many flaws -- that I don't want to get into -- to do that. At the same time, I don't want to call it a disappointment, because I played it through twice, which means I got more for my money than I do with most games.
However, since this topic is about sidequests, then I'll comment on my dislike of the majority of them. As someone has already pointed out, they're basically carbon copies of each other. Go to planet --> clear out bunker --> fight boss dude --> pick up loot --> leave. Also, for the most part, they seem so unrelated to the main plot, that they kind of feel out of place. Especially since you have to travel to different planets than the main quest planets to complete them. It's like, "okay, the universe is in jeopardy, so we need to travel to Noveria. But there's some pirate group that's picking on farmers all the way across the galaxy that we'll stop at first". It just took me out of the experience.
Don't even get me started on the character/party interaction.