Elmofongo: To me the ultimate GTA game is if we combine everything from San Andreas and 4 basically san andreas plus third-person shooter controls,shoot anywhere while driving car,bike and boat, mini games like bowling and watching TV and strip clubs, the friend system, and of course better graphics and gta 4s physics engine
I think that's what they are aiming for with GTA 5. They've officially stated that it covers the biggest area of any GTA game to date. The trailers suggest that they are going back to more fun and variety.
I really liked the Liberty City in GTA4. The first time I walked out of the apartment I was amazed. It really felt like walking around a real city. Then, after some exploring, it became apparent that there wasn't much to do outside of the story missions (Which I enjoyed a lot)