Most have found that text in Titles and Menus is just not as sharp, as with print. Whether BD, or DVD, much can be desired. The results with Video are just not that sharp, and there are limitations. Even if one starts with Vector Type in AI, or PS, when they Rasterize the Vector Art, it just does not look THAT good.
Here are some tips that might make things better:
Alignment - Video Typography Essentials by Richard Harrington
Great Titles with the DV CODEC by Philip Hodgetts
If working in PrE's, or PrPro's Titler, this ARTICLE might prove useful too.
Hope that this helps,
Europe, Middle East and Africa