Below I have five examples. Well tell me how you feel do developers rip off original games or build upon them?
1. Gran Turismo the first real racing simulation game. Both PGR and Forza ripped off GT.
2. Grand Theft Auto the first crime action game. Both Crackdown and Saints Row ripped off GTA.
3. Wolfenstein 3D and Doom the first FPS games. Every other shooter game has ripped off Doom and Wolfenstein 3D including Halo, Half-Life, Counter Strike,etc.
4. Mario the first stand out platform game. Every other platformer has been a Mario rip off.
5. Final Fantasy and Zelda series the first stand out RPG games. Every other RPG steals from Final Fantasy and Zelda.
Well if I replaced the terms: "steal or ripped off" with "improved or build upon". It would sound a hell of a lot more positive.