I would say watch OOT any%, Doom runs(if you have played those games you will think he is playing another game since he somehow is able to jump going against corners in a fast way etc), VVVVVV was insane as well, he did veni vidi vici first try. F-Zero,Monkey ball and those super tight games area always sick as well. And sinister1 always delivers with his runs, so his Ninja Gaiden 1/2,Batman,MTPO are all good. dram55 and his SMW 96 exit is hilariously optimized as well.
My favorite speedrunners are sinister1, duckfist, dram55, Cosmo, Siglemic, funkdoc . you can always trust those guys to beast