Mass Effect is probably the most Shallow action RPG. It focuses a lot more on the action - utilizing cover, aiming shots. No micromanaging inventory, no ammo worries (ammo is unlimited), no attributes (skills and passive talents are the only RPG elements), only 4 different styles of weapon and not much in the way of theorycrafting about which one is better then any other one.
It's very story driven. It has a bunch of side missions (about 60 in all), but they're largely boring "drive here, shoot that" in nature (well, they're entirely that.).. the only one I'd suggest doing if you don't enjoy exploring strange worlds in an ATV is the one that takes you to the moon at level 20. I won't say why, but do it.
There's a lot of dialogue, but the voice acting is good, and almost all the dialogues include some action on the screen, and it's not so much like watching a movie like Metal Gear, you are actually playing the game. The world of the game feels fully realized, moreso then any other new IP game I've seen.
If all that sounds good, then get it, otherwise, find someone with the game and try it. Either way, play it.