Taking Mars

Step into the shoes of a cartoon villain as you devise a dastardly plan to steal an entire planet from an unsuspecting galaxy.

Assassin's Greed - Black Flag: What happens when an assassin gets too greedy and starts dabbling into piracy

Herbal Space Program - enjoy a peculiar kind of interstellar "trips" fueled by particular substances

Duke Pukem

One noble's quest to ensure that all in their duchy know exactly what they had for lunch.

No One Gives Forever - tired of being generous towards friends and relatives, you decide to selfishly start building your economic empire and amass outrageous amounts of wealth just for yourself. Fight for supremacy in the ruthless world of finance in this award-winning business sim.

You know that Wizardry 6-8 have Lizardmen as a playable race? (Some of the Japanese Wizardry spinoffs do as well.)

Super Mario Bras.: Wait a minute, are we actually playing as bras? (You know, the thing that people with boobs wear to support them, or because of societies expectations or habits? Yes, those.)

Edit: Another one:

Dark Son: Shattered Lands: It is the son of some powerful demon that is shattering the lands. You must stop him (or maybe he is the player character).

Thomas Was a Line - stripped-down version of the original platformer.

Garfield Fart

A disdain for Mondays and one too many pans of lasagna equals a whole lotta trouble.

Iron Store - a simple trading sim where you manage a hardware shop.

Garry's Bod

One man, a room full of mirrors and a rockin' bod.

The Watcher 3-binoculars, and people who leave their curtains open are his thing.

Dang! I didn't even realize the difference until now (creed/greed). I always found the title of the game odd, a bit like "Thief's Lust" or somesuch. That's why AssCreed sounded particularly funny, someone is greedy for some ass?

Ok, now I learned a new word, creed = faith (or a confession of faith?). I had to google for the word...

Oh yeah ad that was written like ½ years ago...

DUN DARE

hire and motivate tax collectors

You didn't specify what type of game, so I came up with this:

Let's play a lame: Cahnge a letter in the title of a game and write a synopsis.: Like this topic (complete with the "Cahnge" misspelling), except that (unlike this topic) it's lame.

Alternatively, how about this?

Let`s play a game: Cahnge a letter in the title of a lame and write a synopsis.: Somehow, you need to figure out what a "lame" is, what it means for there to be a title, what "Cahnge" means, so that you can then cahnge a letter in its title. Then you need to figure out what "symopsis" means in this context.