Depends on the Pokemon.
Kyogre probably tastes something like whale, maybe a bit more watery (inb4 Kyogre is a whale/dolphine memers.)
I can't imagine Groudon tasting like anything but dirt.
I'd imagine that Fug is like 90% carapace, so he probably has very little actual meat to him. Maybe the little meat he does have tastes like lobster?
Some Pokémon would taste good and some bad.
There's also Gulpin in the dumplings (?) on the right.
Here's some more art.
Still up because I had to do a chem assignment
No idea honestly, it could be.