Setting aside for the moment that the two really are very different games and probably suffer by being compared to one another directly: I definitely enjoyed SR4 more than GTA V and given the choice to replay one or the other, I'd very likely pick Saints Row despite it being a much leaner game in terms of content and production values. Part of it is that I find GTA V's cast of characters largely repellent, and I don't really care that that's the point, it's not a nice place to spend hours of your time. Part of it is that GTA V emphasized realism in a lot of ways, which led to a certain amount of annoyance, whereas Saints Row prioritized streamlining the things people generally disliked in open-world games (getting around the world, for example) and emphasizing the fun stuff (causing mayhem, shooting everything with ridiculous weapons, flying). And part of it is that Saints Row has a goofy dance sequence and lampoons Mass Effect a lot, while GTA V makes homosexual rape jokes and makes hamfisted points about the inefficacy of torture, mostly just so they could have you torture a dude without overtly making torture porn.
I watched a lot of GTA V streams recently, and I think as a world with stuff to do in it that's not necessarily tied to its story and characters, it's a fantastic achievement. I remember playing GTA V at a friend's place months after I beat it, discovering that the game is actually so much more fun when you forget to do all the missions and just go hunting for hidden packages and letting the spontaneous dumb/hilarious shit that happens in Los Santos wash over you. And despite all my harsh words, I did enjoy my time with GTA V quite a bit. But in terms of an experience I'd want to revisit first, the answer is Saints Row IV, no question.
