Plants vs Zombies started off as a computer game and eventually moved over to mobile. You must defend your home from an endless wave of zombies, using 49 different plants that can grow in water, at night, or during the day. With other tower defense games being focused on the map path, PvZ is a single direction path of destruction.
The game is fun and mini-games help spice it up. That said, playing the computer version first left the mobile version feeling a bit weak. Personally, I prefer being able to disconnect from the internet and play games in peace. With PvZ, the internet connection requirement was something of a turn-off.
If you are looking for something you can let children play on your phone, this game can do the trick. But if you want a game that will give you the tower defense experience you deserve, check out number 3's TDX.