It's certainly subjective. Smash 4's base newcomer roster is my favorite mainly because Mega Man and PAC-MAN--I could not imagine what characters they could do to top that. And for me with Ultimate's base--they didn't. I only learned about Ridley and K Rool through Smash speculation, so I was happy having known the history, but was personally holding out hope there'd be at least one character in the base for me.
And this issue is, I find, it's really, really hard to find big first party characters that I recognize and would personally enjoy. That's the double edge sword of Smash, given how many characters/franchises are packed in, it does make it difficult to see how they can keep topping themselves in terms of character reveals. Even with Smash 4, characters like Rosalina and Bowser Jr. (one of my personal favs) were pushing it in terms of side characters (Bowser Jr. being interesting for me, not for the character itself, but the gimmick of including all the Koopalings). I do think Ridley and K Rool are great character choices, looking objectively, given the under-representation of heroines (rip Dixie) and villains. But since I hadn't been exposed to them in marketing for those franchises*, I had no clue who they were prior to going on forums like these.
*This is a personal claim, not an objective one. Despite absorbing a lot of Nintendo news, I had never came across either character until I was looking at Smash speculation--I first heard of Ridley through GameXplain's video on the subject.