The Creeps! Difficulty levels, high scores, achievements... Although it's not the most challenging TD game, I enjoy the art style and sound effects. Very good intro-TD game like everyone else said (although to me, it can get pretty hard trying to get "perfects").
Yeah Fieldrunners is like the Tetris of TD games on the iPhone, so that's a given. However, the question is between 7 Cities and The Creeps and I have to say The Creeps just has a charming personality to it that I give it the extra point.
I like them both, but if I could pick only 1, it'd be 7 Cities. Both are really superb games though and you can't go wrong with either.
Yeah, I was just throwing Fieldrunners out there as an alternative for someone who isn't a TD fanatic. If the choice is 7 Cities or the Creeps, I would probably choose the Creeps. The characters have more... characteristics. Simply, I find it more visually interesting. Perhaps you should ask yourself if you are more likely to purchase SimCity or the Sims. One has a broad, detached and omnipresent feel (7 Cities) while the other hones in on a more personal level (the Creeps.) But do keep Fieldrunners in mind if TD in it's pure form does not excite you. Also (I have not had the opportunity to try it myself) Defender Chronicles looks promising.
Forget both of them. Get fieldrunners. It is my favorite game in the app store and by far the best td.
I've bought 5 games for my iPhone, 4 of them are TD games. I like many of the 20 or so I've tried (lite versions), but so far, only felt the price was worth it on The Creeps, GeoDefense, 7 Cities, and the new release Defender Chronicles. It is on sale for $2.99 it's first week, ending today I believe, and well worth the price. I never thought I'd pay more than 99 cents for a game again, but I'd trade all my 99 cent apps for Defender Chronicles. It's a blast, and has much more replayability than all other TD games I've played. Here's a review.