Gan-Kon is a fun series. There are cliches, sure, the plot isn't revolutionary, the art isn't breathtaking, but it was worth the pick up.
Fun is the word that best describes this action comedy ecchi romance. This is actually pretty difficult to achieve for manga of this type, since they usually degrade into a shitty fan-service piece or tension filled drama, losing the idea of "comedy" along the way.
The premise of Gan-Kon is decisively fresh. It uses the old idea of "pokemon-partners," monster guys and girls who get contracted to humans to fight one another for some goal. But, it does this well with the twists to the rule, especially the major one around the middle that allows it to both provide fan-service and yet stay true to the plot (without being annoying).
The entire story is also decently paced, with enough fillers to avoid speeding but also manages to satisfy key plot points. It plays out quite like an RPG in fact, with clear "story quest" arcs and "side quest" arcs that occur simultaneously. There's no random "hey, let's just go to a hot spring for no reason."
Most important point: It's funny. The humor is pretty crude, but for a shounen piece, it does the job. I found myself laughing a lot reading this.
Standard, average, pretty girls, wacky looking guys, fit for gods and goddesses. Characters are distinct (except for a couple gods that look alike) and sharp. Background and tone is done adequately, although I didn't get any emotional responses from this series.
Quite average. The MC has guts and perseverance, but relies on plot armor a whole lot. He's also rather dense, but at least he stays true to one girl. Most of the supporting cast are unremarkable. Token glasses braid unrequited love. Token jealous/pesky animal companion. Isana's not "dere" enough. Character growth is rather invisible though. They do get better physically and mentally, but it doesn't feel like they did much to get there.
Read it from beginning to end. Felt pretty immersed, laughed a lot, got a couple kicks out of a couple action scenes, rooted for the main couple. Wished the ending could be a little better though, especially for all the crap that happened.
It was fun, but nothing I'd re-read anytime soon.