The bassist - who quit the band in 1993 after three decades - doesn't believe his former bandmates' upcoming Barclaycard presents British Summer Time concerts on July 6 and July 13 will live up to their iconic 1969 performance at the same venue.
Speaking on US TV channel Classic Rock, he said: ''They are playing to 60,000 and we played to half a million. When we played, the whole of London closed down. It was an incredible day.''
The 76-year-old musician joined the group for the first of their 50th anniversary gigs last year, but won't return this summer as he feels the ''time has gone'' for a permanent reunion.
While he is proud of the rockers' legacy, he doesn't believe they can trump the feeling of their heyday, especially the Hyde Park gig, which ''was one of the greatest concerts ever''.
He added: ''It was a fabulous career. But I've moved on because I've got other things to do with my life now - I've got three young daughters to bring up.''
Bill recently revealed he was disappointed with his short-lived return to the band last November and wished he'd had a bigger part to play.
He said: ''It was great for five minutes because that's about as long as they let me play. I thought I was going to get quite heavily involved because I was led to believe that throughout the year by them.
''It was fun but I regretted not playing more.''