I don't usually like Let's Play-type videos because they tend to be boring (and get pumped out in high volume because they're so low-effort). However, I do watch a fair amount of reviews/analyses.
For such videos, TotalBiscuit is my favorite by far. He tends to be straightforward and honest and isn't afraid to nitpick, but he also recognizes when games succeed in unexpected or subtle ways. Zero Punctuation is entertaining, but too short and surface-level. I like Angry Joe when he reviews bad games, because there the "angry" part can come out and he really tears bad games apart (TWO AND A HALF HOOOOUUUURS!), but I tend to ignore his reviews of actually-good games because instead of being consistently caustic the "anger" manifests as jumping on the hype train and heaping games with hyperbolic praise.
On the next tier down, it's mostly analytical series - things like XboxAhoy's "Iconic Arms". Then there are channels like Errant Signal which are occasionally good but fucking pretentious as hell, what with "ludonarrative dissonance" and "DAE misogyny can't wait for Gone Home 2".
I don't watch much of the obscure bottom tier, but I like Nilsor's videos, especially the Fallout lore stuff. The only problem is that his accent, while sometimes funny, also gets really grating really quick.
As for the worst, I'll jump on the Pewdiepie hate train. Pretty much all Youtubers pander to specific groups, whether it be Errant Signal's appeal to the "games as art" crowd or TotalBiscuit's "PC Master Race" ideology (which I feel is justified simply because there are so many console plebs that PC people need someone to look to), but the average age of Pewdiepie's audience is apparent within minutes of watching his stuff. Also, it's mostly Let's Plays, which are, as I said, probably my least-favorite video format.