One thing I was a bit dissapointed with on GTA4 was the lack of easter eggs and things to find. I understand R* wanting to make the game as realistic as possible but c'mon guys.
I think that in GTA4 and Red Dead R* missed out some great opportunities to add some great little features that would have been awesome...
Like in GTA4 on the helitours the pilot tells Niko that there are lots of sharks in the ocean but actually there isnt any, might sound a bit cheesy but as being a shark fan i would love to have a few scattered around the ocean areas to make things interesting.
I would also love to have a few more creepier areas in the game where the player actually feels a bit on edge as to what might be around. For example in GTA SA on Mt Chilliad there was the serial killer rumour and the big foot rumour. How cool would it be to have a mad man on the loose in certain areas.
These are just a couple of my ideas and i would love to hear yours, happy hunting!