Mini Reviews:
(gonna add more when I have the time. You can choose a different format, just include whether you'd recommend it, yes or no

)
Costume Quest
Type: Comic-style, fun RPG, turn-based combat
Playtime: around 8-10 hours
Achievements: very easy to get 100% on with a guide, few missable achievements
Would you recommend this game?
Yes
Comments: Fun and easy. I also have the addon which adds about 2-4 hours of playtime.
Comic Jumper
Type: Comic-style run & gun 2D platformer
Playtime: around 10-12 hours, slightly more to get all achievements
Achievements: 100% easily possible with decent platforming skills, some grinding required
Would you recommend this game?
Yes
Comments: Great style, especially if you love comics, had fun though I probably wouldn't play it again.
Death Spank
Type: Colorful action-RPG
Playtime: around 10-12 hours
Achievements: 100% easily possible in one playthrough, maybe use a guide
Would you recommend this game?
Yes
Comments: I also have the addon "Thongs of Virtue" - a bit shorter, but easily completable as well.
Game Room
Type: Provides a virtual arcade in which you can place and play arcade games after you bought them
Playtime: 36+ hours to get all achievements
Achievements:
WARNING - Achievement is going to pop when you start this. You can't get all of them unless you spend a lot of MS points to buy new games
Would you recommend this game?
No - waste of money.
Comments: If you are a retro game lover (as in 1970s/early 1980s) you might get some fun out of this. Otherwise, avoid.
Hard Corps: Uprising
Type: Anime-style run & gun 2D platformer, "Contra" clone, 2P online/offline co-op
Playtime: I haven't managed to beat it yet. I find it really, really hard due to limited continues.
Achievements: I haven't gotten any yet (played it for 2h). I assume they are really hard as well.
Would you recommend this game?
No, probably not to everyone - due to the difficulty
Comments: I actually enjoy playing it with a friend sometimes, but beating it will require old-school practice.
Hexic HD
Type: Puzzle
Playtime: I've played it for about an hour, might play it sometimes when I have nothing better to do.
Achievements: Probably medium difficulty and some patience to get everything if you're good at the game.
Would you recommend this game?
No
Comments: Bought this because I felt I wanted a puzzle game, but I regret buying it.
Lara Croft: Guardian of Light
Type: Top-down action-adventure/shooter with puzzle elements, 2P online/offline co-op
Playtime: I think I spent around 12-15 hours on this game, but that included getting all the achievements. One simple playthrough estimated around 6-8 hours.
Achievements: Update: completed the game by now. All very doable, one is slightly time-consuming. One needs an online friend or second controller.
Would you recommend this game?
Yes
Comments: It was great fun, especially in co-op!