I am looking for a bike specific oil. I have read some pretty good review about the GTX (even though it is not bike specific) but in my country the Castrol (moto only) that I used has the same price as the GTX so there is no point on going in that direction. And sadly for the rotella is not available hereIMO, with frequent oil changes, synthetic oils are a waste of money. Forum member Buickguy put over 100,000 miles on his 1987 CMX250. He used Castrol GTX and I believe he changed it every 1,500 miles (approximately 2,500 km). Any good quality oil, that doesn't have friction modifiers will provide excellent protection. All oils that meet JASO standards would work and don't contain friction modifiers. One such oil is Shell Rotella T4 15W-40.
I don't think you can judge how good an oil is by how thick it appears.