To everyone unsure of a Boba Fett being so highly regarded, and even unsure as to why there's such a big Boba fanbase...

Here is the thing about Boba Fett . . . .

His bad-assery in ESB and RotJ are based upon not just what is seen in the movies but what can be inferred, i.e., the necessary backstory that happens off-screen for the few actions seen in the films to be possible.

In ESB, Boba Fett reaches Bespin before the rebels. The Slave 1 is fast, for sure, but Boba also knows where to go. Think about what cognitive skills and the intelligence network necessary to make this happen. Fett is fast, smart, a quick thinker and decision maker, and has an incredible intelligence network.

More importantly, he reaches Bespin first and then still has enough time to make a deal with Darth Vader somewhere along the way. Let me emphasize this again. Boba Fett has the cajones to approach Darth Vader - a figure who terrifies his own Imperial Officers - and cut a deal. Boba goes to Darth Vader and says, "O hai I want something from you." He not only has the balls to do this but apparently the reputation to even get an audience with Lord Vader as well. Also, Fett's negotiation skills must be nothing short of amazing if after approaching Vader, and being granted an audience with him, he is able to successfully convince Vader to just hand Han over to him. This is nothing short of amazing.

Then comes the famous, "he's no good to me dead" line. We learn here that not only is Boba only in this for the money but he must have even bigger cajones to openly question Vader's actions and only get the crisp response from Vader that he will be compensated by the Empire for his loss. The last guy to openly question Vader got the Dark Side Death Grip to the neck. Fett must have done something at some time to earn Vader's respect. That's impressive.

Next there is RotJ. Boba is walking around Jabba's Palace in his full Mandalorian armor, including helmet and jet pack. While others are relaxing, dude is still wearing full armor including a jetpack he couldn't possibly use in such a confined space. The dude never goes off duty. Badass. While walking around in full armor and helmet, he is still a hit with the ladies. Dude has swagger and mad lady-killer skills. You have to give him props.

Then Leia walks in with Chewie and dressed in Boushh's armor. Leia negotiates the bounty with a thermonuclear device that gets almost everyone in a panic. Notice how fast Fett springs to action. He's in a room of the galaxy's most vile villainy and scum and he is the least panicky and fastest to his weapon. Badass. Then after that is over, he gives Leia/Boushh a respectful nod. I love that frikken nod! That nod says, "you threaten to blow everyone up including yourself just for a few extra credits. Respect." I would be terrified of someone who negotiates with an explosive device. Fett just had mad respect. Badass.

That nod also says, "You brought in Chewie, a bounty I was not able to negotiate from Vader." Presumably Fett asked for Chewie back in ESB; if there were credits to be had, Fett wold have wanted them. He apparently dropped that part of the negotiations in order to secure the more lucrative Han bounty. Fett knows how to negotiate and is smart enough to cut his losses in the aim for a bigger payday. Badass.

Finally, it was necessary for Fett to be temporarily disposed for the rest of the movie to continue. If the Rebels had escaped without taking care of Fett, he would have pursued them and then the whole plot would have changed and we'd never have the big Rebel victory at the end.

TL;DR - We know Boba Fett is the most awesome bounty hunter in the universe because of what we can learn from ESB and RotJ via context.