Not nearly as bad as some reviews made it out to be.
In my honest opinion, Overlord 2 is better than the first. I'm not really sure why the IGN reviewer said that the mounts didn't really add anything to the game. Aspects ranging from strategy to instances of power/strength were clearly affected. In addition, I found the graphics to be quite good. Nothing necessarily mind-blowing, but pleasing enough. The sound wasn't too shabby either. Voice acting all around was pretty good, ranging from decent to excellent.
To fully enjoy Overlord 2, you really have to appreciate its comedic delivery. Throughout the game you will be hearing pretty funny dialogue from a myriad of characters. This 'charm' will definitely be a hit or miss, and affect your opinion of the game. Gameplay wise, you are given 4 different minion types (blue, green, red, and brown), all with their own specific strengths and weaknesses. Again, IGN's review said that they perceived Overlord 2 to not be much of an improvement over Overlord 1. I most certainly found this to be false. Overlord 2 had enhanced its puzzles and pacing. Also, I found the story to be more enjoyable this time around (although admittedly, it still wasn't all that fantastic...)
There was much to like about Overlord; I guess you could say I fell to its charm. There are, however, also a myriad of problems with this game. By no means is this game perfect. For starters, there are bugs. Nothing game-breaking, but definitely some weird situations where voice-overs may overlap or minions will be found floating randomly in the air. Also, there's the gameplay (the ultimate hit or miss...). Throughout the game, there were instances of authentic fun...but also moments of extreme frustration. Honestly, Overlord 2 was not the kind of game I could just play for hours and hours...because -somewhere- along the road, there was always some sort of annoying checkpoint/cheap-death issue. For example, you may die to a boss, and respawn miles before it...or there might be a sequence where you'll die, and end up having to replay 5-8 minutes of gameplay to get back to where you last were. This resulted in a few rage-quits for me (AKA: "alright...enough for tonight.......")
The minions/puzzles followed the same hit or miss example. Sometimes I felt as if they were pretty effective and manageable overall. In other instances, however, they were really stupid (practically suicidal). There were also some control issues in this game...I remember particular instances where I was wondering, "I can't believe they actually expect us to do this without developing carpal-tunnel" or "Are you serious?! There's absolutely no way". All this, however, is not saying the gameplay is flawed beyond enjoyability. It's just, for sure, not as great as it could've been.
Still, overall, there's much to like about Overlord 2. Its enhanced look, charm, humor, and moments of fun were well worth sticking through its somewhat lengthy campaign. There were moments where I was authentically frustrated...true. But the thing is, rating a game like this a 6.0 really doesn't do it justice. At the very least, it's a 7.5. Not excellent, but not bad. Somewhat worth playing.