I actually really like Luis Lopez as a character.
However, I feel that a lot of people dismissed his personality, P.O.V. and flavour he brought to Liberty City, because people take one look at the APC, Buzzard, cars with nitrus, Sticky Bombs and Explosive Shotgun, and say "f*ck this, I'm out!", dismissing the entirety of T.B.O.G.T. as "Trying too hard!" and/or having a "Shallow, plastic storyline.", when in reality that is quite a far stretch from the truth.
Also, let me be very clear here. I am not saying that you have to like T.B.O.G.T., nor am I implying that opinions differing to mine should be invalid. Everyone is absolutely entitled to their own opinions. However, dismissing the game on the very outer surface as being hollow and 2D, without opening your mind to exploring beyond the coating, frankly isn't going to form a good well-informed opinion, no matter how you try to spin it.
Personally I thought Luis Lopez blended in well with the city, the other side-characters and added another perspective to the conflicts/tensions among the three protagonists, as well as the antagonists. The nightlife side of things which were hinted at in Grand Theft Auto IV also got fleshed out, and we saw more in-depth how Luis dealt with said lifestyle, and the atmospheres it landed him in. Often with funny outcomes and entertaining scenarios.