I still don't get why all the people who hate the game still post here, but whatever.
As for the game itself, I like it. I've played civ1/2/(SMAC)/3/4 and now civ 5, and have enjoyed each one when they came out. I played some (civ3) less than others (civ4 BtS), partly due to time, partly due to gameplay.
I will say it's different than the past. Some people don't like the new mechanics - fine. I wasn't a big fan of religion when I first heard about civ4. There are some pretty bad flaws in game balance even still after a few patches. That's why you hear a lot of people talking about "potential".
Some of the new rules, most notably the 1upt and diplomacy, really makes the AI flaws stand out. In the past, diplomacy issues never really stood out. AFAIK, nobody really payed attention to diplomacy until civ4. Then in civ4, it was a focal point of the game - you HAD to play the diplo game to beat the game at immortal/deity. But the key is they had the diplo game, and it was obvious. Any flaw in AI diplomatic actions could easily be chalked up to "that's just how it is". But now, they're much more erratic. It's not obvious their true feelings, and so the weird moves that they do just don't quite make sense. It's a decent idea, but definitely still needs tweaking.
And with combat, again, in previous games, AI flaws could often be overlooked due to stacks. They could just churn enough units out so you might not really care that they didn't optimize it. I mean, look at the advantages the civ4 BtS AI gets on deity! If they were a smart tactical AI, they'd wipe the floor with players, just because they can build probably 3X the units. I never made it to that point - I think I tried one or 2 cooked deity games, and I was just creamed. But now, with the unit limits, maintenance, and so on, the game's edge isn't nearly as strong. So since combat depends a lot on tactics, you really notice the mistakes. With smart tactics, you can easily beat an opponent twice your size in civ5. And since the AI's not that bright, you can't avoid seeing those flaws and wincing.
But overall, the gameplay is still there. It's like every other civ in some ways - settlers head out to build cities, a tech tree, some opponents. As people mentioned, the graphics are a notch up from previous games. There's a few really neat additions. But in some sense, it's still a version 1.0 release. There's still some bad bugs in it, and some bad exploits and AI issues.
If you can overlook some of the issues, it's a fun game. As mentioned above, it's backgammon to civ5's chess. Fun to play, a few neat things, and it takes a lot less time to master than civ4. IMHO, it's not a bad game, but if it doesn't get some patch or expansion help, it definitely won't quite have the shelf life that civ4 BtS had. But there's a very strong base - with a few good improvements, it should be a more than enjoyable game for the foreseeable future.