I usually don't write too many reviews on games, but this one deserves it. I will try and be as structured as possible without getting too much into rant territory.
First off is the good. The first say 15 minutes of the game. You start out with a normal story buildup like the previous 2 SP games. You go through the tutorial which seems promising where you learn all of the mechanics of the game(there aren't that many). It is a 3rd person shooter/mob survival game. Basically you just start swinging your melee weapon at the waves of enemies that get near you. The tutorial level gave me the impression that the game would be a different experience than what it was though. On to the bad.
The Bad: Everything else. The art style. The weird 3d characters that remain after the first scenes are atrocious abominations. The game is too short. There are only 5 missions. Each one took me about 30-45 minutes. My playtime is reflective of a whole single playthrough. Although it was a struggle to finish. The first 2 missions were not bad. Combat started getting stale quickly though because you only have like 5 attack moves, which don't vary too much in game from start to finish. Anyways, the AI teammates I had were actually competent(guess this should have been in the good category. Oops.) and were able to resemble a somewhat decent combat force against the hordes of enemies coming at me.
Problems quickly arose during the third mission, and this is where the glaring gameplay faults began to shine, and would continue to shine on and grow until the end of the game. The worst part of this experience would have to be the number of enemies coming at you at any given time-versus just you and 3 AI allies. Even on easy mode, the AI would just get overrun. Trying to go around and revive them became tedious, borderlining impossible. The Main fault is the AI aggros on you way too hard. Mission 3 forwards I spent no joke or exaggeration, more of my time getting hit by attacks that stun, freeze, made sick, grappled, and every other type of stun-lock under the sun than I was able to actually play the game and fight back. It became so frustrating when you have like 20 archers firing their freeze arrows at me and having to quick time action my way out of it, or just sitting there getting wailed on helplessly.
One other note in the bad was there was a distinct lacking of most of the iconic South Park characters. Sure the main ones are there: Cartman, Kyle, Stan, Kenny and the gang, but they were not a very big part of the game outside of the intro to the missions. There were definitely cameos by others (Randy Marsh, Mr. Mackey, Jimbo&Ned) but all were probably in it for just one scene a piece and only deliver like 1-3 lines. If you are buying this game looking for creative storytelling from all the characters like in the first 2 games, I would say avoid this one because you will not get that experience at all.
A final issue I had was somewhat minor compared to the others I have already listed, but the voice acting was terrible. The main characters sounded fine, sure. But as mentioned, your character is the same voiceless one from the other 2 games, and in missions all you hear is the vocals of the enemies. The 6th graders, and preschoolers were definitely not the same as the ones from the tv series or other games. It was like the budget ran out and they grabbed random kids off the street and set them up in a room with a $10 mic. It sounded flat, and the actual dialog coming from them sounded...lame and humorless. While this was not the worst part of the experience, it hurt with the immersion into the game and only made me more aware of how much of a slog a 5hr game can be when it is shit.
To wrap up, it was probably a blessing that the game was so short because I was starting to lose my sanity at the end, but I wanted to finish the story line up to see where they took the narrative. Spoiler: Not worth it. Like some of the other reviews have mentioned, this game is a poor follow-up to the other 2 games that were actually quite good. I would leave this on a strong not recommend. Maybe if it goes on sale for like $5. But even then, know that it will not be a great experience. I hope the developers take this criticism and make a newer better game that more reflects the original 2, because those were actually great games with balanced gameplay and comedy.