Boba Fett is successful at tracking down the Millennium Falcon when the entire Imperial fleet and an army of the best bounty hunters in the galaxy failed.
In the battle at the Sarlacc pit, Boba Fett is the only enemy to successfully strike Luke (with his fibercord whip). I'm not sure, but Fett may be the only character in the entire trilogy to hit Luke with a ranged weapon outside of a vehicle.
Boba Fett is the strong, silent warrior who isn't intimidated by anyone, including Darth Vader. After Vader's "I'm altering the deal" speech to Lando, Boba Fett is the character who's not afraid to talk back to Vader and make Vader renegotiate the deal for Fett's bounty (in the carbonite chamber). The only other characters in the trilogy to speak to Vader the way Fett does are Palpatine, Tarkin, and Motti (who got force choked for his insolence).
In the original trilogy, Boba Fett is the only guy with a rocket pack.
Trying to downplay Boba Fett in the original trilogy is the equivalent of complaining that Batman has no super powers. It's the classic pizza cutter; all edge, no point.