Happy Wars is good; it's just not great.
Happy Wars separates its players into three distinct categories: warrior, healer, and mage. All of them are excellent to play as; though, I prefer the warrior class. Because let's face it: I enjoy fighting people up close and personal. During the game, you can communicate with players with a chat dialogue menu. You can criticize or be nice to people. You can make yourself look like a total narcissist or a complete jerk-off.
Some maps in Happy Wars are creatively well-done, bringing a certain unique flavor to the table that other games generally don't. Airlifts into different small forestry areas; this somewhat reminded me of BioShock Infinite.
The graphics in Happy Wars will either turn players on or off. The artistic style in my opinion, fitted the atmosphere almost definitely. It's almost got a cartoon-network vibe.
The problems that surround this game, though, come from the lack of any true replayability, You have multiplayer conquest, then you have cooperative conquest, you then have a campaign conquest, and finally you have a tutorial conquest. They all do the same song and dance. There isn't much different from one another besides player size. You will get tired of this game, quickly, though it may be a once-a-month fling.
The other huge issue is the abundant amount of technical issues in this game. If your connection fails, or 90% of the people in the current game quits, the match ends with no-one getting any true experience or fulfillment of unlocked achievements. This created a serious issue for me, considering I spent a good two to three hours healing people - then getting a connection issue than losing that option to get the achievement. The game is down-right frustrating like that.
Yes, I am an achievement whore.
Overall, Happy Wars is about the best free-to-play game you'll get on the Xbox. Granted, it's far from great or entertaining: but it's something to try if you have run out of games to play, or nothing to do in general.