Alright, I like action/shooter games and RPGS, both of which these are. Bioshock has much more combat from what I've seen, but a less gripping story. I prefer more fighting and combat but if it's a crap story I kinda feel empty when playing and get bored. But if theres almost no combat... I get bored to tears aswell. So which should I get, or in other words, which will keep me glued to the screen, and if so for how long?

I finished BioShock not too long ago, and I plan on playing Mass Effect sometime later this year. I think if I had to do it again I'd play Mass Effect first... I only bought BioShock because it is so cheap for the X360

I agree with most of what you said Subzer0, but for me they're about equal. ME has the length sure, but nothing in that whole game gave me the creepy anticipation you get in Bioshock when you're about to mix it with a Big Daddy, or start hosing a bunch of Splicers with Napalm.
Bioshock makes up for its length with adrenaline rush, IMO.

Mass effect.