Judith Keppel's £1m win on Millionaire beat the final episode of the BBC One sitcom, which saw the death of Wilson's character Victor Meldrew after 10 years of the show.
Wilson told reporters: "It seems a bit unfair to take the audience away from Victor's last moments on earth."
His agent said the actor was "most upset" by what had happened.
Mrs Keppler's big win - the biggest in British TV history - was filmed on Sunday.
The show's host, Chris Tarrant, denied it had been deliberately leaked to The Sun to take attention away from One Foot in the Grave.
He added, in an interview with GMTV, that he thought the cat must have been let out of the bag by an audience member.
Side switch
One Foot in the Grave had become one of the UK's best-loved comedies, drawing 18 million viewers at its peak.
The death of its central character in a hit-and-run accident had been anticipated for several weeks.
However, early audience figures indicate that 13.9 million viewers watched Mrs Keppel's big win on Millionaire, as opposed to 10.7 million tuning in to see Victor's demise.
Millionaire took 48% of the total audience, while the BBC comedy, starting 15 minutes later at 2115 GMT, attracted 36% of the audience.
Mrs Keppel scooped the £1m prize when she correctly answered "Henry II" to the question: "Which king was married to Eleanor of Aquitaine?"
But more than a million viewers switched sides after she won - with ITV's audience dropping to 12.7 million, and BBC One's audience rising to 11.6 million.
Despite the competition, One Foot In The Grave's overall audience was still one million more than usual.
'Dumbing down'
ITV said it was "absolutely thrilled" with the figures, while the BBC was "delighted" with its showing - and expects Victor Meldrew's final audience to rise by a further million when video viewing is taken into account.
"I'm sure Victor Meldrew couldn't believe it that the figures were so great, despite what ITV tried to throw at it," a BBC spokeswoman said.
"One Foot In The Grave has always been a popular show and it was an excellent evening for the BBC."
The figures add fuel to the battle for ratings between BBC One and ITV, sparked a month ago when the BBC moved its main evening news bulletin to 10pm.
Millionaire presenter Chris Tarrant has denied questions on the programme were made easier to help create its first jackpot winner.
Tarrant said: "The questions are hard. We refused to dumb the question down.
"We said it will happen one night. We always said it would come out of the blue and it has."