It would depend on how it turned out. Could be good, could be terrible. I don't really consider any of the GTA or SR games to be spectacular. They're mostly fun for what they are. GTA4 took itself too seriously. GTA5 just tried to cram too much in there and I feel like the base gameplay just hasn't evolved and was kinda lacking. SR1 and 2 had too many issues to be worth playing (they could definitely use some overhaul and release new versions on a newer engine). SR3 was like a modern GTA3, but with an extra dollop of silliness that was just what I was looking for after GTA4. SR4 was fun but had too much scripted sequences that got on my nerves. But it, Sleeping Dogs, and Just Cause all reveal how limited GTA is gameplay wise now. No you don't have to give people that crazy over the top level of gameplay elements.
I also feel like GTA has not aged that well. I really liked the idea behind Vice City, but looking back now, it was pretty lackluster. Do something really stylized (like Blood Dragon compared to Far Cry 3 for instance). Yes a lot of that was the technical limitations, but all of these types of games tend toward a certain visual style. Even SR's sill stuff still had that general visual look (well some exceptions to that). A futuristic setting could supply that. Like a Futurama esque world. They could even do a sorta alternate history type of setting (kinda like Bioshock or Fallout, only without the apocalyptical angle).
Actually a super stylized noir detective game (that could realize what stuff like Dick Tracy and plenty of others attempted but effectively didn't really succeed at) could be a lot of fun.