We did first person shooters, now what about their cousins, the TPS?

Which IP in the genre do you think is best, and why?

Probably Gears of War.

I also like Spec-Ops: The Line.

I'm gonna say Gears of War. Can't really think of a better third person series. All a matter of opinion of course.

Ah, Spec-Ops was great! Army of Two was another fun one I thought. 

ME is a RPG with shooter elements

I'd like to say Mass Effect, I'm a huge Mass Effect fan, but I personally can't consider ME a 3rd person shooter, even though it has those mechanics. :/

Ohh this is tough one, not super duper tough one. I'd say Gears of War( or Gears) is the best IP in my experience because why not i liked ultra-violent action game with gruesome so much especially my favorite iconic weapon is Lancer AKA the chainsaw assault rifle-Chainsaw Bayonet.

Honorable mentions: Max Payne and WinBack(<psst this one is the old god of third of person shooter which in turn influenced games)

Definitely Gears. Great fun co-op games. Mechanically refined. Always had awesome multiplayer modes, and really pioneered the now popular Horde mode.

As an aside, I'll note that a lot of the titles you've listed here, I don't really consider to be third person shooters. Sure enough, they're third person games, and you do various amounts of shooting in them, but calling them shooters is slightly disingenuous. At least to me. A shooter, in my mind, is a game where the core experience really revolves around said shooting. Games like Mass Effect, Tomb Raider, etc. aren't actually built around the idea of running around and having gunfights. They're built around adventuring, platforming, solving puzzles, exploring your environment, role playing, and so on and so forth. The shooting is just kind of there, and all we really ask is for it to be decent enough to not undermine the experience.

Oh, I forgot about Dead Space. One of my favorite trilogies in video-games.

Factually the best and people who play it like a cover TPS play it wrong.

EX Troopers is another good one. Maybe not best but I got to spread awareness of this great game. On PS3. Region free system. Game despite in Japanese is very import-friendly. I completed the game with no issue.

Lastly underrated as hell but fun as hell. Binary Domain from the Yakuza studio. This has a relationship system and if you don't get along with a teammate they turn into a boss. Depending on how good your relationship is with them by end game determines how many teammates help you fight the final boss. Also has a pretty good story.