Thank you again for your responses.

I haven't played any of the Tropico series, but based upon the reviews, there was a love/hate debate over Tropic 3 and most of the naysayers claimed Tropico 4 fixed most of 3's problems.

I didn't get lost in the Anno series. I bought 1602 when it first came out. I quit playing it because I was in desperate need for 1 iron necessary to build a cannon. 8 deliveries of iron to my warehouse later I still didn't have that 1 iron I needed. My current complaint had to do with Anno 1404.
I got caught up in too much micro-management; found an undocumented mouse command which didn't quite solve my problem with pirates attacking and sinking my ships on automated routes; and so many other issues with having too many goods, or not enough goods because my supply ships had been sunk, that I couldn't actually build new industries or deliver the supplies I needed to in order to continue the mission.
Yes, I could have played the game differently, and accomplished their goals without building an excess of goods to sell, and I could have played without automating anything, but that would have contradicted what the game said I should do. I'm not saying others couldn't or didn't succeed where I failed, but that to me the game didn't live up to its promise or suit my play-style.

Of all the Tower Defense games suggested,which ones are only a little bit more advanced than Plants vs Zombies?

Lastly Civ4... Even with the editor I hated the land masses that were generated; and I always felt like I was cheating when I changed things.
I disliked it when Barbarians built in inconvenient location which were almost always on top of a special resource... destroy the city, destroy the special resource.
I felt the game balance which favored trees was actually unbalanced.
Likewise, even though 'Warlords' introduced new leaders, I only felt like there was one good choice for my leaders qualities and that I was crippled because leaders had three qualities and I always had to leave one critically important quality out.
Because trees were the most desirable thing to have, Engineers could no longer build trees (or hills) as they did in Civ 2. (you could cheat and edit in trees and hills, but not do it legitimately)
Finally, although I liked the concept of a city having an expanded sphere of influence, resources which you couldn't directly effect with a citizen only provided a vague benefit. (trees didn't make your citizens happier or increase production, farms didn't provide food, etc.)