"Ritona" is the Japanese romaji way of spelling the pronunciation of Littner.
If you show a Japanese the word "Littner" they will just read it out as ri-to-na.
Many foreign name spellings get mixed up because of that.
As Kaisos said, English speakers would have no idea what "Tengen Toppa" means, unless they translated the full title as "Heaven Shattering Gurren Lagann" which is still a mouthful.
It's the same thing as "Tenkuu no Escaflowne" being simply named "Escaflowne" along with many other anime.