Ajit has the second biggest opening after Rajnikanth in Tamilnadu and thats why Billa is listed at No.5
According to the DCR from theatres and the reviews it got, Billa is placed at 5. It can move up at replace Mozhi at 4 but definitely it wont drop down with the list of films down below.
Paruthiveeran, Mozhi and Chennai28 are the best films of 2007. The calibre of films that ran successfully apart from these 3 movies shows that Tamil film industry is fast becoming one like Telugu where story or screenplay or performance never matters and its only hero's punch lines that matters the most.
Bollywood is the worst case except for 2 or 3 films.