It's a great tool, I'm using it right now when I'm not slacking off on Rerolled. You can see a sample of the games made with it here:
Unity - Showcase - Gallery - Featured
Beyond a rendering engine and infrastructure for game objects one big thing Unity brings to the table is an art asset library. As a gamer I've always felt that it was a shame folks made art assets for a game that then got buried and died with that game. Obviously you don't want to be playing the next Dark Souls game and see Duke Nukem riding a Maco wielding Frostmourne, but there are so many neutral art assets that people recreate from trees to rocks etc.
Maybe there's a resource like this and I just don't know because I'm not an artist, but it'd be interesting if there was a library of art assets licensed under a GPL-like license where, roughly put, if you use any of the art assets in your game, you have to also share all of your art assets as well.
Right now the asset store for unity:
Asset Store
Is too small to accommodate games' requirements, so when games exclusively use assets from there it's awkward like Pantheon. But you can imagine what it'd be like if the asset store had high quality renderings of every new model year vehiclel, every popular firearm, an assortment of models for every common species of tree etc.