Tommy isn't a rip off of Tony Montana, but he is heavily influenced by him.
Here are similarities between Scarface and GTA: VC:
-Tony and Tommy both kill their ex-bosses (Frank and Sonny respectively) and take their empire
-Both build a powerful cocaine empire
-Their mansions are almost identical
-Malibu Club takes influence from the Babylon Club
-Tony and Tommy both arrive in Florida without any money in a Hawaiian t-shirt
-Last mission resembles last shootout in the film
-3C Apartment is modelled after Sun Ray apartment
-Tony and Tommy have similar outfits
-Both of them have a short temper and are intelligent
-And much more...