I think Pep can be reasonably argued either just inside or just outside the top 10 p4p all time. Saddler is his best win. That should be weighed against his 3 losses to him. All 4 fights were after Pep had a serious accident, following which Peps results took a turn for the worse. He begun his career a remarkable 102-0 in fights contested in and around FW. He was 32-1-1 in fights contested at other weights during this time, the loss being to the formidable and much bigger LW Sammy Angott. To answer your question, aside from Saddler his 4 x wins over borderline ATG FW Chalky Wright stand out. Top tier wins over Famechon, Bartolo x 3 and arguably the GOAT at BW (I rank #3 there), Manuel Ortiz, are supplemented by wins over other world class boxers in Terranova, Lewis, Sierra x2, Graves, Dade, Leslie and Riley.
Anywhere from the lower part of top 10 to the higher parts of top 20 is fine. His resume looks something like this Joey Archibald x2 Chalky Wright x4 (these are massive wins) Pep then loses to legendary lightweight Sammy Angott which ends his 62 winning streak. Sat Bartolo x3 jackie Wilson x2 Willie Joyce Manuel Ortiz a top 10 bantamweight of all time. the plane crash happens around here. Paddy Demarco Loses to the Legendary Sandy Saddler. Willie Pep is now currently 134-2-1. Avenges the Sandy Saddler defeat. Harold Dade Loses to Saddler two more times. If you really like consistency then you'll have Pep really high up on your list. His only loss pre-plane crash was an all time great lightweight. However if you prefer weight jumping over consistency then he'll fall down a few spots. Another thing that will affect how you rate him is how badly you think the plane crash affected his career. I've seen some act like Pep was completely shot after the plane crash or that it didn't affect his career at all. Obviously these are the more extreme examples but you get my point. Pep-Sandler 2 is usually high up on lists of the greatest victories of all time. Unfortunately we have no footage of it. He's also basically the undisputed greatest featherweight. Not many can say that they're the go to number 1 of a classical 8 division. In my heart I would really like to say that Vicente Saldivar is the greatest featherweight of all time but no matter how you look at it he just isn't as great as the Will o'the Wisp. Is Willie Pep's resume impressive? It's impressive enough to be considered the greatest featherweight of all time but when compared to guys in the top 15 pfp it falls short. There's no shame in having a resume that isn't as good as Benny Leonard or Tony Canzoneri.