What red wine is the best sweet wine?

Creme de la creme, and the sweetest - Sauterne but other parts of Bordeaux make some nice sweet wine too - for instance Cote de Bordeaux. German wines in general are sweeter than most.

Very sweet - too sweet for many people and too sweet to drink with almost any food - Spanish Moscatelle de Valencia - GREAT with traditional Christmas pudding - sublime.

Sweet wines in general are expensive so it really depends on how much you want to spend and it depends on what you really mean by sweet.