It's very hard to compare RoN to Civ, since they're two completely different games, one is turn- based, and one is real- time. However, RoN, IMO is like Civ on a smaller scale, ex: you fight battles as opposed to entire wars.
The graphics in RoN are very grandiose, yet the gameplay itself is also very good (and very addicting), the only problem may be your graphics card, mine didn't work when I first got the game (I had to download a patch to get it to work), but the cursor in the game still didn't work, and sometimes the game wouldn't start- up. When I got the expansion, and after game actually did start- up (about once in a blue moon), sometimes it would crash, and I had to attempt to start it again. But, then I got a new computer and it never gave me a problem again.
The trial version seems to be full of bugs or something, I messed up when first trying to install it, and it never worked again (the trial, that is), even though I re-downloaded it, and tried again to install it. So basically it is up to you, if I were you, however, I would buy it, its an awesome game the only problem is the graphics require a great graphics card to work. On the back of my box, it says you can check your graphics cards compatibility on
www.riseofnations.com, so you might wanna do that first.