But it wouldn't be the same game. Look at GTA III, then look at GTA: IV. Two totally different games, but set in the same place. Most fans want Vice City, just to get the feel of how it would be with the updated graphics and physics, and overall gameplay, and count me as one of those fans.
Personally, i dont know alot about paris but the Eiffel tower, and its rainy, cold weather. VC AKA Miami i know is known for the beaches, girls, sun, money, and fast cars. It depends on R*'s view on the protaginast, whether they straight up have him rich and go broke, then work his way to the top, or start broke and come rich and own VC. Who know's.