As said making an game engine is not an easy task. E.g. have a look on the state of my 3das project. Luckily i am in no hurry.

As for giving a headstart you could investigate the following on quake vs delphi:
http://www.geocities.com/jimmyvalava...lphiquake.html
http://www.sulaco.co.za/quake2/default.asp
and if you go for quake do investigate the licensing around that for commercial usage if you want to go that way.

But as said maybe try something smaller first.