I think that this is an interesting question - what characters are more entertaining to watch? I do know that the players are a large part, but in general, which characters do you like to see playing?
For me, most entertaining are:
Ken - the way he is an aggressive yet patient character, also his srk looks cool
Dhalsim - watching a pro dhalsim completely dominate someone by shutting off all their options and stopping them from jumping or doing anything is really entertaining. Also when they use u2 as an anti air (torimeshi).
Hakan - seeing a good hakan do that pressure with the focus dash cancel into normal stuff just looks so cool
Cody - his pressure, in your face normals, crazy links and his JP voice actor all make him really fun to watch
Fei long - seeing a fei with great reactions whiff punish every single move
El Fuerte - pisses me off, no further explanation needed
Rufus - just not very exciting or varied
Seth - the same flowchart stuff gets old quick