The issue I had with 3, (didn't even play 4 as it was basically just a mod of 3) was that at least in SR2 there was some level of normality. If you didn't do anything out of place, the game world, environment and peds would act naturally and go about their daily lives. You would see people working and doing stuff at the airport, driving boats in the sea, sunbathing, etc.
SR3 had none of that. It was impossible to take any of the game world seriously. Why is that a problem you ask? Because messing around and being silly is only funny if you do it in a place that it was not entirely meant for it. If you have peds doing weird Michael Jackson taunts on the street and the world does not even feel like a real living breathing world, the humor is totally lost.
I felt that from SR2 which was amazing, aside from the driving physics. Had the perfect balance of a semi-real world, but had options open to you for silly hijinks.
SR3 couldn't even be arsed to have a day and night cycle. There is no f*cking excuse for that in this day and age. Pretty much everything I loved about SR2 (Customizable melee and power kicks, picking up and throwing objects. Partially realistic looking weapons. Ninja outfits and decent clothing options. The 2 door bootlegger, to name a few.) was totally gone.
There is nothing funny about stupidity that is forced on you as the main goal for the game. It only works when you feel like you shouldn't be doing it. If it is a key objective it just becomes over-used and worn out.
The only things from SR3 I liked was the sprint-dive animation.
It felt like they spent more time on the jiggly tit and purple dildo physics than the actual environment and atmosphere.