What could be called “The Michael Jordan Show” has become prime time’s top-rated hit, as Game 4 of the Chicago Bulls-Phoenix Suns series shot down the second-best rating ever for an NBA Finals telecast.

With ratings up more than 20% compared to last year, the only problem for NBC is that this action series could have a shorter-than-hoped-for run. Phoenix must win tonight to stave off elimination and force a sixth game Sunday.

Wednesday’s shootout swooped in with a 19.8 rating, 35 share in Nielsen, including a 41 share among adults 18-49, the key sales demographic. That household number barely topped the fifth and deciding game of the 1991 Bulls-Los Angeles Lakers series (19.7/36) and ranks only behind Game 7 of the 1988 Lakers-Pistons showdown (21.2/37).

No game in the current series has drawn less than a 29 share and two of the games rank among the top 10 in all-time NBA ratings, with increased interest likely as the finals head toward a climax. The Suns-Bulls series is a shoo-in to blow away last year’s six-game average of 14.2/27 for the Bulls and Portland Trail Blazers and should surpass recent highs of 15.8/34 (Bulls-Lakers) and 15.9 /32 (Lakers-Boston Celtics) set in 1990 and 1987, respectively.

Jordan and the Bulls still have a long way to go in terms of challenging the Magic Johnson-led Lakers or Larry Bird-fronted Celtics, however, when it comes to ratings heroics.

The Bulls have now been combatants in three of the top 12-rated NBA telecasts , tying the Detroit Pistons. The Lakers, with Johnson, were a participant in eight of the dozen highest-rated telecasts from 1985-91, while the Celtics played in seven of those games during the Bird era and an eighth back in 1974. The NBA remains one of the few sports franchises whose ratings have steadily been on an upswing. NBC recently extended its NBA deal through 1998 with an estimated $ 750-million agreement that involves revenue-sharing between the league and network.