I'd love a Mk1 but the wife wouldn't let me have one, no power steering and not "modern" enough.
My overall fave is the Mk2, good looks, decent engines, handles well, goes really well.
I've had a Mk2 16v and a Mk3 16v, and I'd say, if you want comfort and a more modern look, go for the Mk3, but for raw driving fun, the Mk2 16v is much better.
Mk4; look modern, 1.8T engine is good and tunable, but the car as a whole, not to my taste.