Speaking as something of a connoisseur on this subject, I still think the humble and ubiquitous Bourbon is the king of biscuits. Not too fussy, not too plain. Sits in the background not flashy or demanding attention, just getting on with the business of being tasty, satisfying, cheap and plentiful. Just right.
Although having said that, I am also quite fond of those German ones which are like hard rectangular rich teas with a slab of plain chocolate stuck to the bottom. Choco-Leibniz I think they are called. Only problem with them is eating a packet at a time gets costly.