It was basically a mixture between The Stick of Truth and Kingdom Hearts.
It was an RPG with graphics just like the series. You played as Morty but Rick was a permanent party member. The game would basically involve your house (or even town, school etc) as a HUB and you taking different missions that transported you to different universes, gummi ship segments and all in Rick's ship (not clear if gummy segments were just a nightmare-ish part of the dream or if I really think it's a good idea). In each different "world" you'd get a new temporary party member relevant to that dimension/world, some of which you kept for later missions.
I dont remember if it was made by Obsidian, but surely it was, and Roiland and Harmon were fully involved in writing it and voicing it.
Weirdly enough, I distinctly remember a segment of the dream that was more akin to The Real Animated Adventures of Doc and Mharti, were you as Morty would have to button mash in order to lick Rick's balls so you could travel back in time. I think this was because I rationalized that they could get away with this on a game, not so much on a Cartoon Network show.