At first glance I thought the thread said "screaming" not "streaming".
Anyway, for me the let's play-ish type videos I've enjoyed the most fall into a few categories:
1. Ones that make me laugh (nerd3, yogscast, huskymudkipz, dashiegames)
2. Ones that teach me something about a game I'm interested in or have enjoyable commentary that don't necessarily relate to the game (paulsoaresjr, kurtjmac)
3. Ones that give an entertaining quick review of a game (total buscuit, CGR, angry video game nerd. etc.)
4. Ones that play through an entire game I either loved as a kid or wasn't able to play as a kid because I didn't have it or didn't have a good enough PC to run it.
By far the most entertaining ones are videos that make you laugh. If you don't have that talent, then you'll have to have a game that's compelling enough to hold the audience's attention. An example of this would be RockLee Smile's Eryi's Action play through. Even though he's not funny at all, his tenacity to calmly keep working at the game that is kicking his ass over and over is very enjoyable to watch: http://www.youtube.com/watch?v=MBRiX2pYi3I
One idea might to be look at Soli's free games thread here. Do a "free game of the week let's play" or something. Even if it's a short 2 hour adventure platformer game, that's still 8 or 9 videos. Certainly enough to fill a week.
You could even tie that into the upcoming 12 Days of Christmas drive that IGS is doing later this month, picking games from there: https://indiegamestand.com/christmas.php