I recommend the Etymotic Research ER6i. I'm on my second set after the 1st set's wire at the tip finally gave out after about 4 years of use.
Good noise isolation, reasonable comfort, great sound reproduction, most important: easiest on and off with the helmet (Shoei RF-1000 and X11).
By the way, Etymotic, I understood to have started their business as hearing aid designers and manufacturers for the hard of hearing and elderly. For me, that says they should know what their doing, just like Shure (professional sound). I like the Shure's too, but the biggest issue was it was hard getting my helmet on with it, and once on, I barely was able to get it off... nearly had to go to the emergency room because I and my GF feared I would sustain injury if I kept trying (seriously!). I returned the Shure back to the Apple store the same day.