Plecos aren't a clean up fish IMO. This isn't a one size fits all question, ie what size is the tank, what are the inhabitants, what is it you're trying to clean up?
In my planted tank I have Otto's, Cory's and a freshwater prawn that do a great job. Loach's are great, different species for different size tanks but if snails are an issue they are top of the line. For black beard algae Siamese algae eaters are the best I've seen. As far as plecos are concerned bushy nosed do a good job on algae and the only species I've kept that earned its keep. Earth eaters while I wouldn't classify them as "clean up" fish they keep the sand substrate in my bigger tanks clean and no pellets are left after feeding. MTS are also good I planted community for turning the substrate and riding the tank of any leftovers the clean crew missed, however the best at keeping any tank clean and free of debris is me, my python and algae scraper.