A while back I actually did a list of Spider-Man characters with most appearances. Apparently I counted some reprints (https://community.cbr.com/showthread...upporting-cast) and so on. So that list was flawed. Inspired by this thread at Marvel Comics and based on marvel database (https://marvel.fandom.com/wiki/Marvel_Database) I now have a new updated list.
Caveat: The database distinguishes between appearances (and minor appearances) and discounts reprints. I have chosen only appearances (in any case the addition of minor appearances hardly makes a dent on these rankings).
UPDATED with tweaked rankings to make way for rogues.
The list (as of September 2019) comes like this.
1 - Mary Jane Watson - 1074 Appearances
2 - Jameson - 1046 Appearances
3 - May Parker - 766 Appearances
4 - Robbie Robertson - 611 Appearances
5 - Norman Osborn - 597 Appearances
6 - Flash Thompson - 574 Appearances
7 - Harry Osborn - 477 Appearances
8 - Otto Octavius - 440 Appearances
9 - Betty Brant - 428 Appearances
10 - Eddie Brock - 377 Appearances
11 - Felicia Hardy - 374 Appearances
12 - Miles Morales - 374 Appearances
13 - Scorpion (Mac Gargan) - 318 Appearances
14 - Sandman - 300 Appearances
15- Liz Allan - 273 Appearances
In general Mary Jane and Jameson are #1 most recurring. Sometimes Jameson is ahead, sometimes it's MJ. But those two are at the top. Aunt May being a distant #3 is the big surprise since so many think she's oh-so essential. And Robertson being at #4 ahead of what we think of Peter's classic Ditko era cast is another one. This is 616 Continuity and not just ASM. Jameson and Mary Jane are the Spider-Man characters with the most appearances outside of Spider-Man, with Jameson appearing in Daredevil and other comics, MJ cameoing in FF, Daredevil (with Peter), and in the first three issues of Ms. Marvel and more recently Iron Man.
We also need to consider that some of these characters were dead for a long time. Norman Osborn was dead for 20 real-time years but even then he still managed to become the #1 most recurring villain. Doctor Octopus at the very fitting number 8 caught up recently. Harry Osborn was also dead for nearly 20 years.
Miles Morales is an odd figure. He debuted in Ultimate Marvel before being imported to 616 so it's a bit hard to decide if one should count only his 616 appearances or his 1610 appearances when for all intents and purposes that's one continuity more or less. Still Miles Ultimate Marvel appearances is 70 so most of his appearances are in 616. But I thought it was fair to rank Felicia ahead of him even if they were tied since she's all 616 and everything. Eventually I expect Miles to surpass her.
Note I haven't included all the rogues. In general Osborn, Otto and Venom are top three. But going for the rest needs more finagling. Then you have Kingpin where you need to discount his Spider-Man appearances from his overall list (largely Daredevil). IF you can help me, I will update this list.