ive only used uploaded and rapidgator for long enough to really answer this and i can tell you that uploaded is the worst of the 2, i think they might shave 90% of all sales, while rapid probably does 50%
Datafile seems legit but their site is garbage, design is great but its slow and 50% of the time is shows gateway errors.
Keep2share is legit too, great design and amazing features but offer very limited space for new affiliates.
Upstore is legit but terrible ftp system combined with files randomly disappearing had me leaving them
Filejoker not sure about them, i think they are legit but be warned before using their services, they ban 90% of adult words in your filenames so if you already have a adult collection prepare to rename all files otherwise you can't share them via their service.