No GTA IV is not better and it is certainly not more ambitious, it's mainstream.
GTA IV was undeniably good in it's own right but it just felt too stripped down to satisfy me, if you look at the beta pages on GTA Wiki, you will see that it was originally meant to have things like vehicle variety, tanks, planes, unique weapons and countryside, but it was all cut for a mainstream story driven approach. Don't get me wrong, I like a good story just as much as the next person but not when gameplay has to be sacrificed, GTA IV didn't have had bad gameplay like other story driven games such as Mass Effect 2 but I was worried that GTA was going to head down that path.
As mentioned, the gameplay in GTA IV is not bad, but it just feels too stripped down, for example, the most important aspect of a GTA game in my opinion is the vehicle variety, and GTA IV lacked in this area, there are so many unqiue vehicles (Caddy, Cement Truck, Newsvan, Prison Bus, Kart, Mower, Air Ambulance, BMX, Dozer, Towtruck and the Sweeper for example) which could have fit into the New York setting, there were a few unique vehicles (Mr Tasty, Helitours Maverick and the Romero, although that last one didn't have a spawn point, it was only available in one mission), but nothing when compared to previous games and GTA V. The vehicle spawning is also flawed, for example, the Police Maverick and Police Predator do not spawn when the player does not have a wanted level unlike previous games where the Police Maverick spawns at the Police Station and the Police Predator spawns patrolling the waterways like police cars spawn patrolling the streets.
TL,DR: GTA V has better gameplay, GTA IV is too mainstream.
"Too many people like this game, WAH it sucks because of that!!"
V is pretty bad, but IV is terrible.
jetpack removed, small map etc.