Well, the OP asked for Athens...
For a honeymoon stop over I guess you would preferr one of the big chains. If possible get the Hilton. ^ Have never stayed at a better Hilton in Europe(FRA included). The exec lounge is extremely nice with views of the acropolis and so are the rooms. Make sure you get a room facing the acropolis. They have some really nice suites too.
On my three stays I have been upgraded to exec on all thee occasions and I had a look at two of the suites.