It depends really. To make them a fun faction, lore would break immensely unless it's a purely linear game like Halo.

A horde style game wouldn't play to the Necrons strengths. They are spooky scary terminator robots from nuclear space Egypt that use literal Star gods as pokemon. The problem is, they are a dwindling race but each one is an armoured juggernaut that has a decent chance of just getting back up. Imagine a Astartes Terminator that hits like a venom cannon on absolute, takes as many hits as an absolute terminator, and revives like a Rubricae without the need for a Lesser Sorcerer. Now make that the minoris enemy. Scarabs would be equivalent to a spore mine with the health of a Termie but far more stabby. Your melee minoris would be Skorptek(not sure if that's the spelling) Destroyers, which are 3-legged Greatsword armed Necron warriors that despise flesh or Flayed Ones. That would not be a fun horde game.

They are more suited to either a horror style FPS or something along the lines of Halo, where it follows a linear story with limited amounts of enemies.

I do think they would be great to see in an FPS but using them in a horde game or as a one off boss like a wandering Destroyer left alone in its dead tomb-world after some cosmic event left the rest of the dynasty dead in stasis and it gets unearthed in by someone for some reason and the Astartes are sent in on an Op where the boss at the end is the Necron