I am of a certain age where I was brought up on 3 door hot hatches. There was no such thing as a 5 door hot hatch back in the day, so I am firmly in the 3 door camp. I just can't see 5 doors as a sporty profile. Same as these new fangled taxi engined GTD stylee "hot hatches". Again, back in the day there was no such thing as a hot taxi engined car. Dinosaur, I am. 
The Golf GTI has been available in 5 doors right from its very beginnings in the MK1. Small cars do suit 3 doors better. Back in the MK2 Golf days, a lot of its hot hatch competition was smaller again - the likes of the Renault 5 GT Turbo and Peugeot 205 GTI. The Astra GTE and XR3i were the same class size, but still small compared to the current Golf/Astra/Focus.
3 doors on a medium to large size car now is a PITA with wider cars and parking spaces not betting any bigger (the worst I have come across being my Boss' A5). I do my utmost not to park next to a 3 door car, as its doors are likely to clatter my car when the occupants get out.
First and foremost, a hot hatch is practical, and 3 doors are pretty impractical these days due to the width/parking issue.
The Golf isn't small any more, it looks just as good in 5 doors as 3 doors.
Nowt wrong with hot diesels either, now they are actually hot rather than being a 70hp naturally aspirated clattery lump with a trim upgrade. Many people love the effortless torque of a high powered diesel and still having great fuel economy.