Stardust and Super Stardust didn't do anything special at all! Still screens with BOBs moving over it? A low-frame looping animation that moves around the screen with more BOBs on top of it? That's all it is. They did it on the Atari ST and PC too, so it's definitely not doing anything special.
I don't consider a game that fills the full 1MB or 2MB RAM as "hitting the hardware" or anything like that. Making use of expanded RAM is nice, but it's not some special technique.
As for Universe, I'd like to know for sure how they achieved the amount of colours they used in that game. It's possible to change the entire palette several times on the screen, so perhaps they did this? Cut each background image into wide chunks, remapped them to 32 colours (allowing some of the colours for Boris and the other objects) and did this several times for each image, then combined them (creating an odd looking picture at first) then the palette changing trick is applied and the whole screen is using more colours then. This might not be THE way they did it in Universe, but it's totally possible in OCS so anyone CAN do it if they want more colours in their games.
And now, since it seems the cool/redundant thing to do, I'll mention some games other people already mentioned earlier in the thread.
Brian the Lion