I have .177, .22 and .25. Haven't gotten to the bigger calibers yet, so can't speak to .30 and up. I'll rule out the .177 to start. Too light.
Like others stated, it depends on the use; however, if I had to choose one caliber and couldn't ever have another gun, probably go with .22. In the right gun it's accurate to 100 yards with upwards of 30 fpe, yet can be tuned down to 12 fpe for indoor or tight spaces. I have a .25, but it's just too much for tight areas, it really needs a backdrop.
.22 wins in economy as well. Pellets are 1/3 less cost than .25 and more economical on air usage.
as always, my opinion is worth what you paid for it. Take it for what it is, my opinion.