Tom Glavine was 13-8 for the Mets this season. If he retires before next season, his 13 wins would be far the most last-season wins for pitcher who pitches his final MLB game as a Met:
Randy Jones, a former Padres star, pitched for the Mets in his last two seasons and won 7 games for the Mets in his final MLB year.
Randy Tate won 5 games for the Mets in 1975, his one and only season in the majors. Randy was by one measure the worst batter in the history of baseball. He had 41 ABs in his career and not a single hit -- that's the most ABs by any batter in history who had 0 hits. He did have a caught stealing though -- after reaching base on an error. On the mound he wasn't terrible, and it's not clear why he never got another chance after 23 starts for the Mets at the tender age of 22.
Bob Friend won 5 games for the Mets in 1966 after the Mets bought him from the Yankees in June that season, following a fine 15-season career with the Pirates (4th on the Pirates' all-time career win list).
Bob Apodaca won 4 games (and saved 5) for the 1977 Mets at age 27. An excellent reliever for the Mets (a sparkling 1.49 ERA in 1975), arm injuries prevented him from pitching in the majors after that 1977 season. Hardly ready to leave baseball, Bob became a pitching coach in the Mets farm system, and worked with Clint Hurdle when Clint had great success as a minor league manager in Mets organization. It was widely assumed that Hurdle would manage the Mets big league club someday, but it was Apodoca who made it to the Mets as their pitching coach from 1996 to 1999. Maybe the Mets should have kept him -- he's Clint Hurdle's pitching coach in Colorado in this week's National League Championship Series.
Three other guys -- Mardie Cornejo, Mike Bruhert and Joe Crawford -- each pitched his last major league game for the Mets and each had 4 wins for the Mets in their final season. In each of these three cases, that last MLB season was also the only MLB season.