Nothing is perfect but this comes close.
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Pros:
1) It has been attempted in the past and i can't think of a single other game that successfully had multiple protagonists work well in harmony without taking something away from the game play. Each character has their own unique feel to them even though you might be doing the same thing.
2) Truly amazing heist design that build up upon each other in succession.
3) Weapon, Character and Vehicle Control have been vastly reworked since gta4.
4) Possibly the biggest game world to date that isn't empty but has actual content that you wish to explore
5) Amazing graphics, voices acting, even though there is the occasional frame rate stutter.
6) Simply believable and in some cases relatable lead protagonists.
7) Unforgettable story or heists.
8) Incredible re playability and choice at ending.
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Cons:
1) The side missions for the main protagonists can be a bit inconsistent with their expected behavior.
2) Dynamic events are interesting but could be fleshed out more; in particular you have the option to rob an armored car on route and grab a 3 to 5 thousand, mid to late game this score is insignificant. I would have liked to see the armored truck follow a route and make multiple picks ups before returning to it's destination, that way we can map it's route and plan heists the following day.
3) The recruited heist members serve no purpose. Other than the fact that they sometimes accompany you on the main heist missions and more than likely die doing so, they have no purpose. You can't use them to rob a convenience store, you can't use them to rob armored trucks, and some such as the hacker are used in only a single mission. I would have like to see this mechanic fleshed out more.
4) Shared ownership/wire transfers; we all know that there are properties for purchase. It would be nice to see or have the ability for the three characters to be able to buy properties together or to send each other money through their respective banks. Currently the banks and atm's serve no real purpose since we already know how much money we have at all times without having to go to an atm to check.
5) Not much to do underwater. It is fun at first, watching that first shark attack or exploring the underwater expecting to find a sunken ship but it ends up feeling contrived; just there for the sake of being there and not serving any actual purpose.
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While some of you won't even read this and simply judge the score, I don't believe any game is worth a 9.5 or higher because it can always be better. A 7 used to mean a game was worth playing, an 8 meant that it was a MUST play. Giving out 9s and 10s is a sad thing to see when it comes to reviews nowadays.