I owned a few 125 bikes when I was younger. I must say that of all of them the CG125, although not the most interesting, was by far the best. Ultra-reliable, simple to maintain and great fun to ride, if you can find a reasonable one that isn't worn out they are definitely worth having.
However, of all the bikes I have owned the newest bike was made in 1979 so there could be a number of really good models out there, made more recently of which I know nothing about. Presumably though, the newer models all have restricted BHP.