disclaimer: in 1996 my perception and knowledge of BO only limited to Sun TV Top 10 movies......
Muthu and Kuruthipunal were neck to neck, i think in opening weeks in one of the week KP was placed along with Muthu and may also have been #1 in a week (not so sure on this)...... In the year end hits, KP was part of the top 10.......
The fact that Muthu beat KP despite that it was neither Rajini's nor Ravikumar's best (and a good amount of technical flaws esp with camera work and editing) is Rajini's popularity was at all time high at that time.......