Movies have inspired video games for decades now, whether directly or indirectly. TV shows have been a less reliable source; I don't think there's ever been a great TV-based game.

Companies have taken plenty of shots, going all the way back to "The A-Team" and "The Dukes of Hazzard" on the Atari 2600. But as TV producers have gotten more ambitious, so have game publishers. Over the last few years, more well-regarded series — "The X-Files," "Alias," "24," "The Sopranos" — have tried to cross over to games.

And every one has been a letdown. What does it take to make a decent game out of a television hit?

n "Karaoke Revolution Presents American Idol" (Konami, for the PlayStation 2, $39.99; with microphone, $59.99): Here we have just about the perfect match of game and TV show, stretching Konami's venerable karaoke franchise to accommodate Fox's monster hit. The basic gameplay is as simple as ever: Plug in your mic, pick one of the 40 songs and try to follow the onscreen notes and lyrics as you sing along. Your score depends mostly on pitch and timing, so you could just hum the words, but where's the fun in that?

In the "American Idol" mode, your performance is rated by Simon Cowell, Randy Jackson and someone called "Laura" — apparently Paula Abdul couldn't make it — and if they approve you can sing your way from the initial auditions to the season finale. You can also sing with your friends in duets or head-to-head competitions; as always, it is more fun with a lot of different people taking turns on the mic. The song list has a lot of variety, from classics like "Stand By Me" to recent hits like "Sugar, We're Going Down," and there's even an assortment of "Idol"-related tunes like "Breakaway" and (yes) "She Bangs."

Two and a half stars out of four.

n "The Shield" (Aspyr, for the PlayStation 2, $29.99): I'm a huge fan of FX's "The Shield," but I cringed when I heard it was being turned into a video game by Point of View. The TV drama, about corrupt Los Angeles cop Vic Mackey, gains much of its power from its moral ambiguity; as repellent as Mackey is, you find yourself rooting for him. The game dodges any such subtlety.

Mackey and his Strike Team are trying to head off a gang war by any means necessary, including planting evidence, stealing contraband and roughing up (or even killing) suspects. If you bend the rules too much, your "heat meter" fills up, ending the game. There are a few different ways to deal with perps but the execution is so sloppy that the action is more frustrating than fun.

The "Shield" game will disappoint admirers of the TV drama. One-half star.