Please note that this is more of an examination of overall "quality" than "quantity" (i.e. which decade had the most TV series and films produced).

1960s: All three seasons of The Original Series (1966-1969)

1970s: The Animated Series (1973-1974) and The Motion Picture (1979)

1980s: The Wrath of Khan (1982), The Search for Spock (1984), The Voyage Home (1986), The first three and a half seasons of The Next Generation (1987-1989), and The Final Frontier (1989)

1990s: The final four seasons of The Next Generation (1990-1994), The Undiscovered Country (1991), all seven seasons of Deep Space Nine (1993-1999), Generations (1994), the first five and a half seasons of Voyager (1995-1999), First Contact (1996), and Insurrection (1998)

2000s: The final two seasons of Voyager (2000-2001), all four seasons of Enterprise (2001-2005), Nemesis (2002), and J.J. Abrams' Star Trek (2009)