Tower Fantasy
Kingdom Rush is a mostly-well-crafted tower defense game. I mean, I could essentially end the post here. It doesn't go too far beyond what you'd expect from a modern tower defense: you can build towers of varying melee and range effectiveness, you can upgrade them with money you earn from defeating enemies, you can follow alternate upgrade paths for different unique abilities, you can use out-of-combat points ("stars" you earn by completing levels) to upgrade your upgrades so you can upgrade while you upgrade. You have a hero unit, selectable from different options (with different strengths and weaknesses), who can level up during combat.
What makes Kindom Rush noteworthy is, basically, that it's well-made. It's easy to control, it has a shallow learning curve - up until the end - and it's polished with a moderate coat of fun, from cartoony animations to game-industry in-jokes. There are plenty of unit and upgrade options to play around with, so it never really feels repetitive. And, although I didn't get into it myself, there is a wealth of end-game content to explore in the form of bonus mini-campaigns.
But, the game isn't without its share of issues. The last couple missions ramp up sharply in difficulty, such that many previous strategies no longer work, and there isn't any real direction on how to improve. Replaying a level in a more difficult mode disables certain features, turning the game into a puzzle where you have to find the one or two possible tower setups that will work. There are a couple of balance issues that just seem unfair, like the Lich, which infinitely spawns skeleton minions that count toward failure if they reach the end of the lane, but don't yield any rewards when they're killed. And it's a bit disappointing that the extra bonus missions (which constitute almost as much content as the main game) don't open up until completing the core story -- until which time, levels only progress in a forced, linear order.
These irritations are really only remarkable because the rest of the game is just fine. Not excellent, but certainly not bad, either. Kingdom Rush does very well for itself within the established mold of tower defense; but its potential is ultimately limited by how comfortably it still fits inside that mold.
Better than: Majesty: The Fantasy Kingdom Sim
Not as good as: Defender's Quest: Valley of the Forgotten
It does help: that the game is full of classic references, like tesla-tower dwarves yelling "Toasty!" when you upgrade them.
Progress: Finished the main campaign on Normal.