In order to have an expression of irony, there needs to be some kind of juxtaposition between the fact that the game is new, but styled like an old one.

Primordia is simply a new adventure game that evokes the look, gameplay and general feel of one made in the mid-90s, with a moody atmosphere and a serious, sincere story.
There is no irony here. The game's overall effect would be no different if it actually had been released in 1995.

For an ironic (at least in the hipster sense) usage of pixel-art retro graphics, look no further than Fez. This is a game that deliberatly looks kind of like a platformer on a system like the SNES, but it uses a central game mechanic that would have been largely impossible to do on that sort of hardware, is infused with modern pop culture references and even has gimmicky stuff like that puzzle consisting of a QR-code, all of which draws constant attention to the fact that it is, in fact, a new game.

Retro City Rampage also fits into this. A game with the basic structure and gameplay of GTA 3, but with graphics, characters, themes and various mechanics based on NES-era titles. Add to this the numerous references to and parodies of both old and recent pop culture, and you do have an overt case of irony.

You mean that shitty film where characters constantly go "Hey, look at us! Our situation is totally following the rules of a slasher movie!" Yeah, really subtle.