Since the 1977 season (The Modern Era since that's the 1st season after the NBA/ABA Merged),the following teams have won the NBA Finals:
Los Angeles Lakers 10x
Chicago Bulls 6x
Boston Celtics 4x
San Antonio Spurs 4x
Miami Heat 3x
Detroit Pistons 3x
Houston Rockets 2x
Dallas Mavericks 1x
Philadelphia 76ers 1x
Portland Trail Blazers 1x
Washington Wizards 1x
Seattle Supersonics 1x
So pretty much, in the last 36 NBA Finals....19 have been won by the Western Conference and 17 by the Eastern Conference. Pretty even
The late 70s Ran By: Western Conference 2-1
The 80s Ran By: Tied 5-5
The 90s Ran By: Eastern Conference 7-2
The 2000s Ran By: Western Conference 7-2
The 2010s Currently Run By: Tied 2-2
Just my 2 cents