Blimey, thats a tough one. I'm looking at options for my Mk1 (distant) project. I would have liked the 2.8VR6, quality engine but probably too heavy. 1.8 G60 is another option but I suspect are rare as rocking horse sh1t. 1.8T is a viable option, especially in a year or two whereupon I think there will be a few more available for a reasonable price.
I'll be interested to see how people vote here and what they feel makes a good engine, as its not always just about the performance...........................