For me Civ 5 was the biggest video game dissapointment i ever experienced, so obviously I'm biased. But if if you liked the complexity and the empire creation feeling of civ 4, then civ 5 is probably not for you.
If you don't mind a desastrous AI that sends workers and unguarded great generals to the front lines, if you don't mind having to move several units every turn that keep getting in the way of eachother, if you don't mind that diplomacy feels shallow and random, if you don't mind that building takes forever and is unrewarding, if you don't mind that many features have been removed, leaving you with less to do, if you don't mind several sloppy implementations such as a useless civilopedia or mere picture popups when you win, or the lack of available information, and most importantly, if you don't mind playing a tactical wargame instead of an empire building game, then civ 5 may appeal to you.
Regarding multiplayer, I didn't try it out, but from what I've heard it basically comes down to who can click the fastest, as turns are simultaneous and there is no movement delay for units that moved at the end of the turn like in civ 4. And since you can't move once you finish your turn, apparently all players sit out the timer, making the game slow and boring.
And hexes... there has been a big hype about these awesome 6-sided shapes. Personally I couldn't care less if civ plays on squares, hexes or circles! Imo it is pretty telling that this superficial "innovation" is regarded as one of civ 5's best plusses.
This turned into quite a rant, I guess. Told ya I am biased.