There no successful coins other than bitcoin. The second largest coin is 5% of bitcoin's market cap. The third largest is 1%. It gets rapidly worse from there.
If there is ever a successful coin other than bitcoin (unclear, but maybe) it will take new approaches, not anything like any of the current alts.
Personally I don't believe hash algorithm even matters very much. By focusing on that you are getting distracted from anything that does (or at least might) matter.
You are the one that does not understand the big picture. Why was Dogecoin successful at all and has beaten Bitcoin in daily transactions several times? The answer is
market penetration.
A currency is useless without high market penetration. Guess what algos give the highest market penetration? GPU.
When people try to CPU mine and earn 1 penny a day due to botnets, most people cease to bother doing so, and the coin dies from lack of interest.
The future of PoW, if GPU only can't be achieved, is Myriadcoin style coins where you can mine with anything and receive some kind of reward.