One of my favorite games of all time, even after all these years...
Don't let the cartoon-like 2D animation trick you - this is a game that requires considerable strategic planning several moves in advance. The number of powerful weapons (or lack thereof, depending on your game settings) only adds to the strategic choices. Shoul I use a Ninja rope,swing over a cliff, and then drop a banana bomb? Should I release an exploding sheep over the deep chasm to destroy an opponents worm? Should I fire a Magic bullet instead, eliminating a worm half-the-map away? Or should I conserve my high-power weapon(s) and go for a skill shot on a grenade? The strategic possiblilites are endless. The Ninja rope is particularly useful, as it allows you to swing over cliffs, or into crevices, thus being an efficient mode of moving your worm. The ninja rope obviously factors into the gameplay strategy, as well as low gravity, jetpack, etc (if applicable).
Both the single and multiplayer aspects of this game can be tremendous fun. With multiplayer, you're obviously facing another human and communication can be extended beyond the "I'll KILL YOU"s and "I'LL GET YOU FOR THAT"s that are yelled from your worms.
Deathmatches can almost reach impossible difficulty when you're in the later levels. It took me quite a while to beat some of the later matches, due to the uncanny skill the computer has in them to kill you if you are the least bit exposed (not to mention being outnumbered). That said, the deathmatches are a refreshing challenge, and give you a great sense of pride upon completing them.
The missions and training are a nice addendums as well. Missions, like deathmatches, get difficult and often require forethought and creative thinking.
I prefer WWP over Worms Armageddon, soley for the superior single player. It is still one of my favorite games of all time!