I think you will find a vast array of opinions on this one. I would stick with the factory recommended viscosity and use a 100% ester based synthetic if possible. If not, at least a high quality synthetic.
You need a good quality engine oil of the correct viscosity (see owner's manual) which meets the JASO MA standard. Any recent motorcycle-specific motor oil should meet that standard, but read the statements on the bottle.
There are a wide variety of choices. Any of them will get the job done.