Lots of simple cores would be inherently better.
The Cell processor was never used in any other consoles, and the IBM Roadrunner supercomputer using them ended up being replaced by Cray+AMD hardware.
1 https://kotaku.com/5885358/why-skyrim-didnt-play-nice-with-t...
Our current programming paradigms don't adapt well to massive parallelism, except for some small classes of "embarassingly parallel" problems (e.g., make -jN).
My guess on Phi is that it wasn't a big win over fewer deeper cores and so there was not much market. This might change things a bit.
The downside (or upside) is that they're desgined for running Forth, and are not x86 compatible.
http://www.greenarraychips.com/home/documents/greg/PB001-100...