Update: while reading this wiki entry I found that you need to quote your alias only if you are writing it directly on the prompt. On the alias file you don’t quote anything. In fact, you don’t need to modify the alias file by hand because emacs writes it for any alias you define on the prompt.
(This is mostly a personal note but it may be useful to somebody else)
I’m not sure that everybody knows (the manual version I have doesn’t mencion it) but to configure an alias for eshell is as easy as this:
On the .eshell/alias file just add
alias ls ls -la $*
This is a taken from this blog post. You can read there a more lispy way of doing it.
Also, take a look at this interesting this wiki entry