I don't understand this, the reviews of it were amazing

"We all knew GTA 4 would be a great game and sell millions of copies, but I didn't expect it to shame pretty much every other game I've played this generation." - VideoGamer

"I could go on and on about why Grand Theft Auto IV is one of the best games we've ever seen and why even folks who are easily offended should play it, but that would be pointless. The only thing you need to know is that you have to play this game. Period." - IGN

Yet I've spoke to people who've got it and they're not that impressed. Some user reviews say it's boring and stuff. So, is it worth buying?