I greatly prefer the Belgian beers in general. In my view they are brewed for a market where sipping an excellent product is the norm, whereas in the UK most drinkers look for something that they can down several pints of at a sitting.
At present I have at my disposal - Piraat (as mentioned), Trappistes de Rochefort (11.3%), St Bernardus Abt 12 (10%), Delirium Nocturnum (8.5%), Gulden Draak (10.5%), and some Chimay Blue in case any others run out.
I'm also very fond of the John Martin's beers (mainly, I think, brewed in Scotland, but to the Belgian taste and strength) - Gordon's Special Gold and Gordon's Christmas. John Martin, by the way, commissions the Belgian Guiness mentioned earlier in the trhread, and it comes in at 8%ish (and in my view, is superior to any other Guiness).
The "holy grail" is, of course, Westvleteren, but as it's only available by persoanl atendance at St Sixtus Abbey near Poperinge, and by appointment - and then only a couple of cases can be bought, it's about as obtainable as hens' teeth.
But - juts to show that I'm not against UK brews totally, I do like Ma Pardoes Ruby Mild, and I'll tolerate a good Reverent James if it's kept well.