Wow... I'm actually more annoyed with all the complaining about the Pokemon than I am about Ridley...
In regards to Greninja: OH NO GUYS! We got one of the most popular Pokemon this gen and the most popular final evolved starter since Blaziken... HOW... ABSOLUTELY... TERRIBLE... I'm currently drinking a microwaved coffee cup of laundry detergent because I can't handle this...
In regards to Pokemon Trainer: I feel like it was a necessary cut. Programming wise, Pokemon Trainer was actually 4 characters in one (yes, "Red" had programming too) and Sakurai mentioned that if anyone was cut it would most likely be due to technical reasons. Both games run at 60 FPS which is pretty impressive and all the transformation characters were a drag on this in Brawl. PT's problems were made worse because switching was forced if you died and pretty much necessary in match because of the stamina mechanic. They dumped three characters to program and kept the one that was by far the most popular. This was a decent trade off in the grand scheme of things and I don't doubt Sakurai looked into a number of options before coming to this conclusion.
In regards to the changes made to Olimar/ZSS/Sheik: Again, I feel like these were due to the limitations of the 3DS but fans should actually be ecstatic about these changes because it shows that Sakurai has a much different approach to considering characters this time around. In Brawl, characters were largely cut because they ran out of time to add them. With this game, Sakurai is going out of his way to make sure as many veterans come back as possible. ZSS/Sheik could have easily been cut. It would have been two less characters to program but instead he chose to keep them in to appease their fans. Olimar probably has 3 pikmin instead of 6 to help keep the 60 FPS smooth but, again, he chose to not just simply say "screw it" and found a way around it, just like he promised back in August. The only "technical" veteran left is the Ice Climbers and you can bet that they'll be coming back. Like these three characters, they might be different but Sakurai is definitely going out of his way to make sure that they stay in.
In regards to Mewtwo: The Pokemon roster currently stands at 4 and Brawl technically had 6. We just lost two first gen reps when Brawl had 5 so we're now down to 2 in the starting roster. If Jiggs and Mewtwo come back, it'd still be one less than Brawl. Also, notice the HUGE emphasis on Mega Evolutions this time around. Who was the first Mega Evolution shown? Who has an entire movie dedicated to them? Who is one of the ONLY TWO POKEMON who got two Mega Evolutions? Who is the most wanted character AROUND THE WORLD and has been one of the most popular Pokemon for ALMOST 20 YEARS? Holy crap... and there's actually people B'AAAAAAAAAAAAW-ing right now because Mewtwo was "totally disconfirmed" because Gredinja was in yesterdays' trailer... I mean... c'mon... seriously?
I have a lot of thoughts on other characters too that I'll share later. The bottom line is that I think Smash fans should be very optimistic about how this roster is going to turn out and that this Direct actually put a lot of concerns I had about a number of veterans to bed.