You can drive drunk in both games (I think
I've played all the 3D GTAs too, and I have both SR and SR2.
For me, I was really looking forward to GTA4, and enjoyed it very much, but about half way through, the plot lost it's edge, as did the missions.
I think Rockstar rested on it's laurels a bit too much with GTA4, and having completed it, I prefer all previous versions (including the very average San Andreas).
So much so, I sold GTA4 as soon as it was complete, without really wanting to complete all the little extras.
As for Saints Row and Saints Row 2, the first one was a great effort, despite it's problems, and the second one was a marked improvement in almost every way.
I've completed Saints Row 4 times I think, and I've already completed Saints Row 2 twice since it's release.
More importantly, both versions of Saints Row are still on my shelf, and will no doubt get another outing before the year is out, whilst GTA4 is long gone.
Even the new downloadable episodes on XBOX Live aren't enough to make me go and pick up a second-hand version.
I was really looking forward to both GTA4 and SR2, but I personally feel that GTA4 dropped the ball and could have been a lot better, and Saints Row 2 was everything that I wanted GTA4 to be, and more.
Because of this, I am really looking forward to the next version of Saints Row (should there be one), but I'll need to be convinced that GTA5 will be worth bothering with.