1. Los Angeles Lakers - San Antonio Spurs
These two teams have the most dominant in the NBA this millenium with 3 and 4 championships respectively. The Spurs lost to the Lakers in the 2001 and 2002 playoffs and the latter went on to win the title both years. In 2003, in David Robinson's last season and Manu Ginobli's first season, the Spurs broke their duck against the Lakers and went on to win the title. In 2004, Derek Fisher's famous .4 shot effectively ended the Spurs' reign but the Lakers fell apart during the NBA Finals against the Detroit Pistons and the Shaq-Kobe tandem was broken. The Lakers were never really good after that and these teams didn't meet in the playoffs till the 2008 Conference finals where the Bynum-less Lakers beat an half-fit Manu Ginobli and the Spurs only to lose to Boston in the Finals. We had the Shaq-Duncan matchup, and the Kobe-Bowen matchup. And don't forget the NBA's leader in charges, Derek Fisher against Tony Parker. They may resume their rivalry this year.
2. Phoenix Suns - San Antonio Spurs
This rivalry gets beat by the Lakers-Suns one because of Shaq-Kobe, but by a whisker. I remember when Stephon Marbury made that shot to beat the Spurs in the first game of the 2003 playoff matchup which they ultimately lost. They met again in 2005 in the Conference finals and the Spurs prevailed. In 2006, the Mavericks prevented their impending matchups and they beat both the Spurs and Suns only to lose to the Heat in the Finals. 2007 was the height of the rivalry. Game 4 of the Western Conference semi-finals featured Robert Horry knocking Steve Nash into the scorer's table at mid-court. Boris Diaw and Amare Stoudemire got off the bench and were suspended for the pivotal Game 5. The Spurs went on to win that series and pretty won the championship with that series. 2008 saw Marion leave the Suns and Shaqtus came to town, initiating his own playoff rivalry with Tim Duncan. Spurs' coach Gregg Popovich worked the 'Hack-a-Shaq' to perfection and the series was over in 5 games.
3. Los Angeles Lakers - Phoenix Suns
Three teams own the three biggest rivalries. The Lakers and the Suns met in the playoffs in the 2006 and 2007 post-seasons. Can you forget the series where Kobe and the Lakers went up 3-1 only for them to be whitewashed in Game 7? You had Kobe going up against his nemesis, Raja Bell and well, the whole Suns team. Phil Jackson and Mike D'Antoni had a lot of disagreements including a time when Mike said Phil called a timeout after he had called one and 'disrespected his players'. The rivalry has lost most of the Suns suspects; Marion, Bell, Diaw and D'Antoni are gone but their absence is made up by the presence of Shaq. Shaq against Kobe four times a year? No one on the Lakers can guard Shaq even though he's not the same. Both teams are running squads, so more often than not, their games will be fun.
4. Detroit Pistons - Cleveland Cavaliers
Michigan and Ohio are basically rivalry states in sports. You have the famous Buckeyes-Wolverines duels. Ever since Lebron James came to the NBA, Ohio has had an NBA team to match Michigan's. They met in the 2006 conference semi-finals where they lost in seven games, even after winning three consecutive games. Lebron means more to this team than any other NBA player and his Cavs could not overcome the best NBA 'team' in Detroit. The next year, Lebron led his Cavs to beat the Pistons in the conference finals. Who can forget his heroic Game 5 performance where he scored the last 25 Cavs points?
5. Cavaliers - Washington Wizards
This rivalry is probably unlikely because the teams met early in the playoffs multiple times, to be specific, three straight years. The Cavs returned to the playoffs in 2006 and beat the Arenas-led Wizards. Both Lebron and Arenas were emerging. The 2007 was not close as the Cavs swept the Wizards. The 2008 first -round matchup was famous for the Lebron James - Deshawn Stevenson (who?) duel. First, Deshawn called Lebron 'overrated'. Lebron responded saying he responding to Stevenson would be like rap icon Jay-Z responding to a one-hit wonder like Soulja Boy. The Wizards stayed alive in the series with a Game 3 blowout which had Stevenson doing Soulja Boy's 'I can't feel my face' routine with Soulja Boy himself in attendance while his song was blared from the
Others: Spurs - Dallas Mavericks, Houston Rockets - Utah Jazz, Orlando Magic - Detroit Pistons and a bonus, Boston Celtics - Lakers
Playoff matchups I'll like to see -
First round: Lakers vrs Suns, Cavs/Magic-Pistons, Miami-Hawks, Houston-Portland
Second round: Lakers/Suns vrs Houston, Spurs vrs Nuggets
Conference finals: Lakers/Suns/Houston vrs Spurs, Celtics vrs Cavs
NBA Finals matchup I'll love - Celtics vrs Spurs/Lakers. :-D