I’ve only played Metal Gear Rising: Revengance or the XBOX 360 (not sure how it plays on Steam), but I enjoyed it. The sword gameplay is satisfying and the bosses are unique and challenging.
I hear from my bro that Mass Effect 1 has a great storyline and some decent controls, but I’ve seen more fun coming from revengeance because of absurd game play.
Alternatively, wait for the Summer Sale and get both ME and MGR.
Another thing to think about: You may be better off buying the ME trilogy pack on Origin when it goes on sale for ~$10. But I’m too lazy to calculate that right now. XD