Total War is a real-time strategy game. Civilization is turn-based. That sums up most of the difference right there. (Both are excellent games in their particular genres. I would give them both a try.)
To me, watching the reviews for Civ Revolutions has been fascinating. There seems to be widespread agreement that this is pretty much a game that should be scored in the 7-8 range, for being a lot of fun but not having all that much depth. Yet quite a few of the "big" gaming sites have been throwing out some suspiciously high scores (IGN also gave the game an 8.8 score). Hmmm. Makes you wonder what's going on behind the scenes, eh?
There's also a 9.5 review out there from something called "Tom's Reviews", which is so clearly a piece of viral marketing, it's just hilarious to read. Here, take a look:
http://www.tomsgames.com/us/2008/07/09/civilizationrevolution_review/
The whole process has been fascinating to watch. The evidence is really starting to pile up on the whole review issue...
End of 2008 totals: Wii 42m, 360 24m, PS3 18.5m (made Jan. 4, 2008)
