Dungeons & Dragons casts the same sort of shadow over role-playing games (and that's all role-playing games ever produced, whether they be tabletop or video games) that Superman casts over superhero comic books. If it's a role-playing game, it's playing Follow the Leader with D&D.
Recently, more experimental games have broken away from it by having more loosely-defined and user-contributed rules; My Life With Master is one such example.
Champions was the original point-buy roleplaying game. Originally, that made Champions unique; but nowadays point-buy is the preferred method of character generation among tabletop gamers. This means that a majority of roleplaying games out there (including, amazingly enough, D&D) are now playing Follow the Leader with Champions.
Warhammer 40,000 began as a spin-off of Warhammer set In the Grim Darkness of the Far Future!, with just about everything that appeared in Warhammer Fatnasy having some futuristic counterpart. While the setting has since matured and has in fact overshadowed its predecessor, 40k has gone on to inspire other works - compare its power-armored Space Marines, psychic and technological Eldar, and skittering hordes of Tyranids to the power-armored Terran Marines, psychic and technological Protoss, and skittering hordes of Zerg found in Starcraft. This inevitably leads to arguments and flame wars when gamers don't realize that 40k is Older Than They Think, such as when one reviewer accused THQ and Games Workshop of ripping-off Gears of War for the game Space Marine.
Besides video games, 40k and Warhammer Fantasy helped spawn other tabletop wargames, most notably Warmachine and Hordes which are ironically enough made by Wizards of the Coast, the publishers of Dungeons & Dragons, which of course helped inspire Warhammer in the first place.
For the record; the many variants of Powered Armor are based on Laserburn's GZG Japanese Powered Armor◊. Which existed 7 years before Warhammer 40,000.
Starship Troopers, the novel, codified Power Armor, Bug War, and Space Marine as tropes, period, in 1959. It is not the Ur Example, which may be the Lensmen series of the late 30's. If told those Laserburn minis were meant to represent the Mobile Infantry of Starship Troopers, they'd be entirely appropriate. The MI even packed mini atomic rockets on Y-shaped frames of some kind.
