I got them both last week. I think I've beaten Pokémon Mystery Dungeon: Gates to Infinity (the story, not 100% completion, which is impossible), but I haven't played Luigi's Mansion: Dark Moon yet. I'm still playing the first game.
And I'm kind of disappointed in Pokémon Mystery Dungeon: Gates to Infinity. Even though Pokémon Mystery Dungeon: Explores of Sky is a sprite-based game and that Gates to Infinity is a 3D game, I think Sky is much better.
My main concern is that Gates to Infinity pretty much just trades all of the good stuff that Pokémon Mystery Dungeon Games typically have just for better graphics, that's it! All of the previous Pokémon Mystery Dungeon games used sprites and were all in a Gen 3 style world, and Gates to Infinity is all 3D and uses 3D models with almost no sprites whatsoever, which is pretty good.
But the good stuff stops there. In the previous Pokémon Mystery Dungeon games, you could have all of the Pokémon available up to that point. In the Rescue Team games, you could have all 386 Pokémon available at that time. In Explores of Sky, you could have all 493 Pokémon available up to that point except Arceus. But in Gates to Infinity, you can only have 144 Pokémon. And most of them are from Generation 5 with only about 20 Pokémon from all other Generations. And did I mention that there are more than 144 Pokémon in Gates to Infinity? There are, but there are some Pokémon that are in the game that you can't even have! What kind of crap is that? And speaking of Arceus, it doesn't even appear in Gates to Infinity, which means that it a Gen 4 Pokémon and it HASN'T EVEN APPEARED IN A MYSTERY DUNGEON GAME YET (or even its move, Judgement).
There are also less dungeons in this game than Sky.
EDIT: I think I underestimated this. I was only really writing about the Adventure Mode dungeons. There are also Magnagate Dungeons found in "Discover a Magnagate". There are A LOT
of Magnagate Dungeons. Even just the demo version of Pokémon Mystery Dungeon: Gates to Infinity has 54
Magnagate dungeons! That's just the demo and not the full version and that's a lot. How many dungeons do you think are in the full version? Over 100? That's way more dungeons than previous games had.
But the reason why I praise the Mystery Dungeon games the most is because of their exciting, intense stories. I think Pokémon Mystery Dungeon: Explores of Sky is not just the best Pokémon Mystery Dungeon game, but the best Pokémon game of all time because with the best story ever and so many gameplay options, I can't get enough of it. As for Gates to Infinity, the story was good, but it was very SHORT, especially compared to Sky, which had a very long, intense story that got enhanced even more with its Special Episodes. And when I was disappointed over the pre-ending story's length, I thought the post-game story would be better. I was very wrong. You only visit ONE DUNGEON for story purposes post-game while in Sky, you go through, like, ten. Yes, Gates to Infinity has some good new gameplay mechanics and all, like ranking up your moves, which is good, but that's not really my concern here.
Pokémon Mystery Dungeon: Gates to Infinity also has a very flawed Job Mission system. In Gates to Infinity, you could only do ONE JOB MISSION AT A TIME while in previous games you could do up to eight jobs at a time. And Gates to Infinity really makes you do jobs to death. You might probably have to just do jobs for six days or more until the next main story segment. In previous games, you probably had to do jobs for only three days or less. I'm sorry if I'm getting a little too technical.
Look, if you want to make a new game, you can't just buff up on one thing like graphics and leave the other stuff alone or take stuff out. You have to buff up almost everything in the game and definitely not take anything out. And the thing that really
makes me mad is, think of the system that Pokémon Mystery Dungeon: Gates to Infinity is on. It's on the 3DS and previous Pokémon Mystery Dungeon games were on the DS or Game Boy Advance. Think about the 3DS for a second. It's a brand new Nintendo system that's much more powerful than the DS with more memory and storage and better hardware and bigger games (by that I mean file size). And Gates to Infinity is on the 3DS with the other Pokémon Mystery Dungeon games being on the DS or GBA. There's absolutely NO ESCUSE
for Pokémon Mystery Dungeon: Gates to Infinity to have less stuff than previous games if it's on a more powerful system. That's just horrible! Even in Pokémon Rumble Blast you could have all 649 Pokémon up to that point except Keldeo, Meloetta, and Genesect and it has pretty much the same 3D graphics and everything as well as it also being on the 3DS. And Pokémon X and Y will probably have over 750 Pokémon. And did I mention that almost everything in Pokémon X and Y will be in 3D (by that I mean 3D models), Pokémon, the world, everything, with almost no 2D sprites? So, yeah, you get my idea.
Also, by looking at the models in Pokédex 3D Pro and Pokémon Mystery Dungeon: Gates to Infinity and comparing them, you can see that in Pokémon Mystery Dungeon: Gates to Infinity, the developers reduced the number of polygons that each Pokémon model has compared to Pokédex 3D Pro.
So even the graphics in Pokémon Mystery Dungeon: Gates to Infinity are worse compared to other games/apps.