I would prefer dotemacs to the others.
It reflects both the
~/.emacs.el as well as the folder
~/.emacs.d/init.el approach while init and init-el feel less precise for this purpose.
init could however be used to point to
init related questions (e.g. How to change default minibuffer message?). This can be solved either in Customize or through initialization file changes, yet deals specifically with emacs initialization.
Following the other answers I have to revise my opinion.
dot-emacs or .emacs (to avoid ambiguity for dotemacs) or init-file seem best to me. Even though
.emacs is deprecated for
.emacs.d\init.el (or at least the latter is preferred) it is still part of the name for the init-file so could be applicable.
Other options still feel potentially ambiguous to me.