To the OP, a lot of factors go into the judgment of "bokeh", not least of which is personal opinion. Remember it's not a fair fight to compare lenses of vastly different focal lengths or maximum apertures. There's plenty of reviews out there showing test shots of similar lenses between Zeiss, Canon, Nikon, Sigma, etc. It's easy to recognize and embrace the best lenses for this, but when looking to more affordable options, it's even more important to scrutinize more carefully and let your own eyes be the judge.
Also, with the advent of ever sharper lenses emerging on the market, I think this factors into the quality of blur. I respect Charlie's opinion, but I think his comment that the Sigma Art bokeh being terrible was a bit of an overstatement. It's different, yes. It's certainly not as smooth as a 50 f/1.2 or a 50 f/1.0. For some people bokeh seems to be a pass/fail test where the result must either be the best or the worst. No in between.
How you process your images will also impact the smoothness of the blur. I'm talking about sharpness, not negative clarity. For instance, when I shoot an image with a blurred background using a very sharp lens, in post I adjust sharpness locally where needed. Global sharpness adjustments will tend to give harder edges where you don't want or need them.
Am I the only person that doesn't like to describe blur as "creamy"? It just sounds like something that should be poured from a blender.