There are so many, this is a difficult question to answer.
The Casino complex has some beautiful rooms/hotels with a lot to do round it, and is quite central, however there are also very nice hotels with great amenities around the outskirts of the City of Perth.
From experience, have stayed at the Parmelia Hilton twice, loved it! Beautiful Hotel.
Also stayed at Perth Sheraton for overnight. Coming from Karratha, heading to East Coast.
I really needed to slip between the silk sheets, as was exhausted! Got an excellent night's sleep, in readiness for long, early flights, across our beautiful Country!