The most reliable brand of Jet Ski is the brand Yamaha.
Yamaha Jet Skis are a bit more expensive than other cheaper models but the Yamaha Jet Ski I have has been very reliable for 7 years now.
I highly recommend buying a Yamaha Jet Ski if you're looking for a long lasting and very reliable Jet Ski.
Yamaha manufactures other high quality and reliable products as well.