I've been playing Saint's Row on my 360. I like it a lot. One thing I like a lot better about it that San Andreas is that dying is a lot more forgiving than San Andreas ever was. I walked out of the hospital and still had my weapons. Targeting is a lot easier too. That always was a major pain in GTA.
Only thing missing is the atmosphere. I never played GTA3 so I don't know but in Vice City I really felt that I was in Miami and in San Andreas I felt like I was really in Los Angeles(Darn, I cannot remember what the fictional name of Los Angeles was)
I don't have that feeling in Saint's Row. One thing is cool though is watching the passerby. Some of them actually stop and tie their shoes. Now that's cool! I also like being able to restart a mission in Saint's Row. GTA could be pretty unforgiving there too.