If only Deus Ex Human Revolution and Alpha Protocol could mate and have a child...
Alpha Protocol has an amazing dialogue tree system that is probably the most detailed tree system I have seen to date. Rarely have I seen a game keep such detailed tabs on everything I do. On top of that hacking computer terminals, reading up on personnel files, and gaining both positive or negative rep with people actually provides you with fun bonuses that help you on the mission.
The game unfortunately is very rough around the edges when it comes to combat. Often it is difficult to stick behind cover and the AI detection system is kind of unpredictable. Sometimes enemies see you, sometimes they don't.
There are a lot of similarities between Deus Ex's gameplay and Alpha Protocol which is why I compare them. If only Deus Ex had the amount of RPG elements Alpha Protocol had with the solid gameplay.