First of all, I feel that Esam beat Dabuz because he's a better player and lost to ZeRo because Sheik is better than Pikachu.
Second of all, keep in mind that what I said about Pikachu is not meant to be a comparison between Pikachu and the entire cast, but rather only the best characters in the game. For example, let's just look at a couple of the top tiers here for a moment. When I say Pikachu lacks finishing power, I mean that relative to the other top tiers, Pikachu's most powerful moves are not as strong as that of other top tiers. For example, in one of Esam's matches against ZeRo we saw Pikachu land the second hit of Thunder and Sheik survived at about 126%. At that same percent, Sheik could read a jump and Uair it, read an airdodge and use Vanish, or throw you offstage and use Bouncing Fish. No amount of DI would save you from that. Rosalina has Luma, and I don't think I need to explain how powerful Luma is.
When I say Pikachu is not as fast as the other top tiers, I'm not talking about his running speed or airspeed. I'm referring to a couple moves such as Fair and Nair. There's no denying these are great moves, but relative to other top tiers, they're not as fast, safe, or powerful. For example, there's Sheik, Luigi, and ZSS just to name a few characters that have better Fairs and Nairs.
Lastly, in regards to damage output, it's not bad at all. But, again, and I can't stress this enough, relative to other top tiers it isn't great. All of Pikachu's smashes deal a good amound of damage. DownB, neutralB, Ftilt, Nair and Dair all deal a good amount of damage. However, moves such as Fair, Nair, Utilt, and Quick Attack, which are his combo tools, don't deal a fair amount of damage in my opinion. You can string those moves all day, but there are other characters that can get the same results by putting in half the work because they only need to land half as many hits since they dish out twice as much damage.
Now, Pikachu is OUTSTANDING at racking up damage, but some characters can just do it better. I think Pikachu is a top tier character, and one of the best in the game. In order to analyze a character, everything you look at has to be analyzed in the context of where it stands relative to the other top tiers.