Twenty years ago was the 30th anniversary of the creation of Spider-Man, and Marvel celebrated throughout the year.  Plans for the year were summarized in the December 1991 issue of Internal Correspondence, the precursor to ICv2, based on presentations at Marvel’s sales meeting for distributors.  A Spidey event was planned for every month of 1992, including a traveling Spider-Man museum display, Spider-Man character appearances around the country, a nationwide Spidey-party in retail stores for which special kits were sent out.  Editorial material included a special edition of Amazing Fantasy #15, the first Marvel Masterworks for Amazing Spider-Man, special editions, and bookshelf releases. 
There was also an article in that issue of Internal Correspondence about a James Cameron Spider-Man movie planned for 1993, so not all the plans came to pass, but there was a lot of promotional activity and a substantial publishing program supporting the anniversary.
Among the events for retailers was a 30th birthday party for Spider-Man held in conjunction with the Capital City Distribution Sales Conference in Madison, Wisconsin.  We reproduce below the coverage from the June 1992 issue of Internal Correspondence reporting on the event, which was held in early May.  Sorry for the photo quality—they’re scans from b/w printing.
Were you there?  If so and can share some recollections for publication, send them to  comments@icv2com
And now, here’s Spider-Man’s 30th, from 1992:
The long-awaited Spider-Man 30th Anniversary Testimonial Dinner took place Monday evening, and no one was disappointed.  The room was beautifully set, including a Spider-Man cake, Spider-Man bisque, and Spider-Man wine glasses on each table.  On the way into the room retailers were presented with Marvel tins with a Stan Lee autographed Spider-Man hologram, courtesy of SkyBox International.
Following dinner, remarks were made by [Capital City Distribution Co-Founder] John Davis, Peter David, Spider-Man, Tom DeFalco, John Romita, [Marvel CEO] Terry Stewart, and Stan Lee.  Capital and Marvel had purposely kept Stan somewhat in the dark as to what was planned for the evening.  He was quite surprised when Spider-Man dragged him up to the stage where he was praised and lampooned by each speaker in a sort of combined testimonial and roast.  David, as we've come to expect, was hilarious, and the exchange between Romita and Lee over whether Lee was a picky editor or Romita a perfectionist was especially touching.  To say a good time was had by all would be an understatement, as it was, without a doubt, the best event ever held at the Sales Conference.
(L-R) Spider-Man, Stan Lee, John Davis
To cap off the program, Davis presented Lee with a lead crystal engraved plaque that reads, "To Stan Lee on the Thirtieth Anniversary of his greatest creation, Spider-Man. On behalf of comics retailers everywhere, thanks for making it all possible."  Davis revealed that the cover of the dinner program retailers had found at their plates was an exact duplicate of Lee's plaque. Upon receiving the plaque Lee said a few final words.  "This has been one of the best nights of my life.  Thank you all.  Excelsior!"
The Marvel editorial presentation followed dinner.  Marvel had set up a special sound and visual system featuring four slide projectors, two video projectors, and Skip Dietz.  The four screens illuminated with slides showed different images, making for an exciting presentation.  Dietz talked about editorial projects that we can expect from Marvel for the balance of the year.  One announcement that brought applause from the crowd was the revelation that Marvel will be doing a Ren and Stimpy comic book.  Then the crowd got really loud when Dietz announced that his presentation would be followed by a showing of four complete episodes of the popular cartoon.  Retailers who attended the presentation were given a Spider-Man 30th Anniversary print featuring the artwork of John Romita.