Eh, only in certain areas. Jedi combat after all is all about using the Force-you're anticipating your opponent's moves, finding advantage in terrain, protecting yourself from the environment, and looking for opportunities to attack all at once; sure, some Sith (Sidious without question) have an advantage in using the Force, but most Sith and Jedi seem pretty evenly matched to me. It's worth noting that Maul and Dooku out-duelled their opponents in TPM and AOTC; Maul barely used the Force in an attacking sense at all, and Dooku's Force attacks were relatively effective against Anakin, and not effective at all against Obi-Wan and Yoda except for once in ROTS. Sidious is really the only Sith Lord we see carry a fight exclusively through use of lightning/telekinesis/etc. Also, Vader uses telekinesis fairly sparingly against Luke, although you have to consider that Vader is aiming to capture Luke by isolating him from the potential for escape in TESB. The notion that Sith > Jedi when it comes to Force-based combat is pretty much limited to Sidious and possibly Vader. Jedi don't seem especially inclined to do so, but their Sith opponents don't necessarily gain all that much from their inclination to attack using the Force.