Vadriel
Bite my shiny metal ass!
I concede that I don't know everything about the Jedi, and that there's more to them than I know...however, it really depends on the situation.^ this.
A fully trained Jedi in his prime would make short work of an entire Protoss Dark Templar society without much thought. They're just that powerful. I'm not saying the DT's arn't beasts, I'm just saying against a fully trained Jedi 1v1 they stand no chance.
Sit them in a room together and say "Fight!" and sure, the Jedi MAY win. Give the DT a chance to use its stealth and the element of surprise, and the Jedi will get absolutely slaughtered.
I just can't see how any Jedi can win against a telepathic entity that can rob him of his abilities, unless he catches the DT off-guard. Being cut-off from the Force would cripple a Jedi...and it's not a stretch to assume that a DT could do it.
Honestly, I'd love to see a fight like that. It'd be really interesting, to say the least. They're actually fairly similar concepts, just one is better at raw power while the other is focused on trickery and evasion. I still think a DT mind could just flat-out shut down a human...the difference in mental abilities is like comparing a black widow spider to a dust mite.
On a large-scale sort of thing, like one camp invading the other, the win goes to whoever attacks. Jedi attack, the DT's would be wiped out before they knew what hit them...same with the other way around, Jedi wouldn't know there were any DT's around until every one of them simultaneously discovered a warp blade in their throats.