My suggestion : don't base your choice of engine on the language. You learned Delphi, you can learn Javascript or Python or Lua or C#.
Unity is excellent, XNA is good (if you can stand lower-level code). Those are the ones I know and love, there's surely other.
There are sooo many Engines out there, Delphi limits it down a bit.. but you're right, the language is not that important.. (I really don't like some of them though)
Unity - seems to be THE candidate at the moment.. powerful and fast growing in popularity.
(And I really like e.g. the idea of developing for the I-phone..)
But it is script driven.. ; I guess it is very good for e.g. first person shooters / games with big levels/landscapes.. (I'm more into 'creating/moving some simple meshes around'-kind of stuff

)