Ulfric achieves nothing without the Dovakiin.
Neither does Tullius and the Legion.
1. Leads massacre against people of the reach.
Unless you believe that "people of the Reach" only includes those now known as Forsworn, then this statement makes no sense.
Ulfric led a Nord militia in the service of the Jarl(s) of Markarth (Igmund, his father, or both depending on when the father died) that participated in the retaking of the hold after a Forsworn uprising. As to the allegations of massacres and other atrocities taking place, many eyewitnesses and survivors of the events in question pin the blame as much or solely on the Jarl(s) of Markarth, not on Ulfric or others who fought there on behalf of the city's Nord rulers. Go to Markarth and ask around.
2. Walks into Solitude unannounced and challenges the king. There is no mention of the High King accepting the challenge or putting up a good fight back
You might also want to go to Solitude and talk to a few people. The court mage, for instance, will tell you flat out that Torygg accepted the challenge. No one anywhere denies that a challenge was issued AND accepted under the established tradition for such things.
And if Torygg couldn't put up a good fight in his own defense after accepting... well, that really was kinda the point, you know?
3. At the beginning of the game Ulfric gets caught. Hardly an act of a great warrior.
Yes, because no soldier worth his salt has ever been captured by enemy forces after being ambushed and outnumbered. *rolls eyes*
It is only through the Dovakiin siding with the Stormcloaks that he is able to achieve any success
And so we're back to that. It's only through the Dovahkiin siding with the Legion that Tullius is able to win the civil war, so using the intervention of the Dovahkiin to claim that either side is/was weaker than the other is pointless.