GTA 4 not only took itself way too seriously, but also did a horrible job of telling its story. It's a shame this is still such an alien concept for developers, but when one of the most important things is that the story should never be contradicted by the gameplay. It's all well and good for Niko to lament having to lick the local small time crime boss's boots just to survive another night, but it's a tad hard to take seriously when he can spend several in-game weeks doing nothing but running over old ladies, pushing police officers down stairs and baiting the cops into city-wide car chases purely for shits 'n' giggles.
San Andreas was far, far worse in that department. Niko was a video game protagonist in terms of skill and resistance to injury, but most of his power was simply on the level of "Can kill dozens of people before being shot dead." You mostly wondered why he was worried about Roman's debts when he was earning so much money.
The big problem is in San Andreas when CRASH is able to hold the murder of a cop over CJ's head for the whole game. The guy will have killed more officers than some towns have in their police force by the end of the game, to say nothing of the literally hundreds of gangsters (from small time street thugs up to La Cosa Nostra), innocent civilians, government agents, and possible aliens in human disguise that he slaughters. In gameplay, CJ could likely blow Tenpenny and Pulaski away at any given time. They couldn't keep Sweet in prison because CJ could just one-man army the whole joint (and if you play well, you get yourself an Apache helicopter as well before Sweet gets released). You may very likely get arrested and jailed for causing millions of dollars in property damage and hundreds of deaths, only to get released with a bribe no sweat.
The problem is much worse when mere minutes after the game establishes that you have to obey the corrupt cops to avoid getting pinned with a murder charge, you violate everything that is established.
The same thing could be said about damn near any game, though. You could spend all your time in Skyrim
literally picking flowers. Lots of people use MMOs as little more than a virtual form of the stock market. For me, it really comes down to which between San Andreas and GTA IV has the better characters and gameplay, and San Andreas wins on both accounts.
Roman Bellic? Irritating fucker who always called you to take him out on dates to titty bars when you're trying to rob a bank or evade the police. Niko himself? Serious, angsty, and a little whiny; his best moments were when he was being a smartass to the various dickheads in the game, his cousin most especially. That's not the Grand Theft Auto I grew up with, and while change isn't a bad thing, this was an example of
bad change.
Compare to CJ: CJ was serious, too, but funny, snarky, and much more intelligent than his background would lead one to believe. San Andreas also gets nice nods to both Vice City and GTA 3, plus its own original characters like The Truth, Woozie, and even that snake Ryder had their awesome moments. It had more from the start, more content, more places to go, more to do, more to see, and an ending that's NOT fucking depressing as hell.
Either you go thru with the deal, and piss off Kate so bad she never talks to you again...and Roman dies at his own wedding, or you don't do it, and Kate gets gunned down instead of Roman at the wedding. Either way, Niko ends up losing the one woman that he had an actual, legitimate connection to and leaves him with a huge fucking void in his life. Niko ends up just like he was from the start: depressed and pissed off. That's how I felt when I beat GTA IV, too: depressed and pissed off.
GTA IV wanted to be more of a serious crime drama in a series that was never serious to begin with. Shit got real, but it got too real, and the game suffered for it. Story aside, GTA IV is a solid enough game and does have some good entertainment value, but its still lacking the sheer variety San Andreas had, so even in that mark its still, to me, inferior.