To put it simply, the game under delivers. But, allow me to go into further detail.
The good
Funny
As a South Park fan, you can expect jokes everywhere. From mundane items to elaborate quests, you'll find references to your favorite characters and episodes throughout the entire game. Everything you love about the TV show is there.
Simple
The mechanics are straight forward. You pick your class, pick skills as you level, perks as you gain friends, equip items as you get them and do quests you receive.
The bad
Easy
With a combat system like FF, where you just point and click, once you get to level 3-4, battles become ridiculous. At worse you kill any mob in two hits but, most of the time, you can simply one shot anyone. Be it with an upgraded skill, weapon of your own level or summoned aid.
Game design
The game design is flawed. There are several things that bothered me but I'll list a few.
Once you've done a few quests, you've done them all. There is no difference between one battle to another or one quest to another apart from the inside jokes.
You get a lot of junk throughout the game. This junk is mostly funny items you pick up. Problem is, these accumulate VERY fast. After a few fights, you are encumbered with dozens of these.
To sell them? You have to double click each and every one at the shop. If there are stacks of items and you wish to sell them in bulk, you have to press a button with your mouse for every stack before selling it. Frustrating.
There are other minor things you may notice. Such as pointless option between walking and running. Walking is too slow and you'll find yourself holding shift the entire game.
Map
The map shows you waypoints you've encountered and known quest destinations. If you have a hint about visiting X to get side quest Y done, you're gonna have a bad time.
The map will not show you where X lives, even if you've visited him before, and with rows and rows of houses on the map, all looking the same, you are SERIOUSLY gonna have a bad time. Not a fun game if, for every other side quest, I have to check a walkthrough online or go through every location on the map.
Bugs
Although not great in number, these can sincerely break the game.
During combat, and some actions, you get screen prompts on what to press. A few of these are incorrect on the PC, rendering some of skills useless.
It didn't bother me too much because I simply used others (game is easy, remember?).
The game broke when I had to go through an advanced tutorial where I was to learn a new ability. I was not able to go forward until I looked online on what I really had to press.
Conclusion
It seems the point of the game was to provide a long and entertaining South Park episode. But with broken gameplay, it just didn't cut out for me and I had to uninstall the game after a few hours of gameplay.
People might enjoy a Let's Play of this rather than playing it. That way, you avoid the terrible gameplay but, at least, have a few good laughs.