Personally, I didn't like the Mk4 when it came out. At the time, I thought Mk3's were ace.
By the time I could finally afford a decent Golf, the Mk4 had grown on me so much that I bought one.
It's not a rocket (its a 1.8 non turbo), but with my dropped suspension and super wide tyres it handles nimbly now. 0-60 in just over 9secs aint too bad either. Hopefully the remap I'm planning will bring the 0-60 into the 8.x second range. I love it.
Not too sure about the Mk5 yet. Maybe its a grower too.