If your using the 100% stats screen to gauge if you completed everything in GTA V your doing it ALL WRONG. The 100% stat screen only require a fraction of what you need to do. Here the list of things you can do in GTA V. There over 127 mission total which include 69 story missions and 58 freaks/strangers. Then you have 57 random events to find, then you have miscellaneous things which include collectibles and playing darts. You also have 59 hobbies and past times which include races and triathlons. After all of those are done you can buy properties as well own all weapons and their attachments and buy all vehicles which should take you a while since money is somewhat hard to come buy if you don't know what your doing. Like I said some people just stop doing things after they are checked off in the 100% list like they stop doing stranger or freaks after the first 20 are completed or only do 14 random events when their are 57 to look for. Check your social club account to see what you have completed. I say GTA V has WAY MORE to do then Red Dead.
GT- EndingEye - Patriots, Lakers, Dodgers, Galaxy & Kings Fan Kobe Bryant 81 points V.S. Toronto Raptor 1/22/06 Historic
If you exclusively play the story missions then GTA V is a little longer than Red Dead, probably 3 hours longer. I finished RDR in 25 hours while GTA V took me 40 hours, but this is from first-time-taking-it-slow playthrough
*Raises Fire Emblem, casts flame resistance spell, wears varia suit, equips flame terrenial, and goes under fallout bunker* Punished Snake approves...maybe?