Which Old Games?    

From 80's to 90's  -  we don't encourage rebooting too near games, as the subject will kinda loose it's meaning somehow.

Which Hardware / Platforms?  

The games can be from any platform, PC (Mac/Amiga/Atari ST/Coco/Tandem - whichever), Console (all consoles) or Arcades (all arcades).

Does it need be a full  clone? 

Nope.  You can achieve the feel of the original game, but it can be totally different in terms of visuals and sound.  It could also have added mechanics (that's up to you to decide).

Can it be a full exact clone?

Absolutely.  You can opt to keep it 100%  clone.   It's perfectly fine as well.

Note:  if you have more questions - feel free to add as comments so we might get to answer them or expand this material.