Majestic 13

MAJESTIC 13 is miniatures-agnostic tabletop wargame where you command an elite team of alien hunters in a secret war to protect the Earth. Designed to play solo, co-op, or as an adversarial skirmish game, MAJESTIC 13 is created by Adam Loper and Vincent Venturella for 1-2 players.

From the book: "To the public, the modern era of alien encounters started in Roswell, New Mexico, on July 8th, 1947, with reports of a downed alien craft, which were quickly retracted and replaced by the story of a weather balloon. The public remains suspicious but accepts the story and moves on. Conspiracy theorists claim the government absconded with alien bodies and technology and hid everything from the people. Both stories are, of course, wrong."

Use any modern soldier miniatures you'd like for your team, and any kinds of weird creature models for the alien monsters you'll fight. Enjoy a deep campaign system with random mission generation and planned special missions, too. Keep upgrading your team members that survive each mission, and bring out new clones for the ones that don't.