I never touch a single LP that didn't get linked to me by somethingawful. That may make me an elitest, but they are honestly the best, particularly if you cherrypick from even among those.
Reccommendations time:
Some of the best Let's plays that i've seen have come from TheDarkId, who does things in a screenshot-and-text format. He's currently doing Nier [http://forums.somethingawful.com/showthread.php?threadid=3382650], And I have to say, though it is a break from his usual style of doing games that are godawful like Drakengard [http://lparchive.org/Drakengard/] (You should seriously read that one though, that game was fucked up in SO MANY IMPOSSIBLY INCREDIBLE WAYS), he does a really brilliant job of cutting out the nasty parts while making good fun of them (Nier's gameplay was frankly mediocre) and presenting the really really good parts (Characterisation, story and atmopshere) as close as you can get to the real thing.
Indeed, it was his opinion that changed my mind about that game and caused me to buy it so I could experience it myself (I did not regret this - Nier is a very unpolished gem, but a gem nonetheless)
Also, for something a bit different i'm going to reccommend the ongoing adventures in the land of pen-and-paper DnD by Wolfshirt/Syrg Sapphire [http://forums.somethingawful.com/showthread.php?threadid=3273056] (It took a while to get into, but I now avidly follow this as it has truly fantastic moments)
If looking for another laughable romp, and honestly rather short LP, the recently finished Let's "play" of Link's Awakening [http://forums.somethingawful.com/showthread.php?threadid=3387459] (Play in this case meaning "break so far backwards it inverts") was a great thing.
edit: You might want to wait for this to be archived for ease of access, but there is one let's play that holds the crown for the longest running LP to actually get finished. And the fact that it's probably the best damn written game and LP i've ever seen certainly doesn't go amiss for making Planescape: Torment [http://forums.somethingawful.com/showthread.php?threadid=2206352] one of my favourites