There is no <tbody/>
element in that table, remove the /tbody
axis step and your query works totally fine. See "Why does my XPath query (scraping HTML tables) only work in Firebug, but not the application I'm developing?" for details.
Additional hint: XPath also supports single quotes for strings, so you don't need to escape the double quotes.
This XPath expression will return the element you're looking for:
//*[@id='ranking_table']/div[2]/table/tr[1]/td[1]