Why NTR-Rajinikanth failed to do wonders?

Sr Ntr ruled the industry unopposed even when young stars started showing their power. His charisma was such that there was no second coming for him. He continued in the same vein right from the start till the end of his career. He used to transform himself by keeping up to date with the trends and endeared himself to the youth. 

During that time Rajinikanth created a sensation in Kollywood. His films got dubbed even in Telugu and got a good response. During that time P. Narayana Rao on his Nava Shakti Pictures banner produced a film titled Tiger with Ntr in the lead. The story had another role of hero's friend and when he tried to look for another actor equivalent to Ntr, all the actors already starred with Ntr. 

So the producers thought of casting Rajinikanth in that role. Thus Rajinikanth got the chance to share screen presence with the top star like Ntr. Rajini's fights and style attracted viewers and also the scenes between Ntr and Rajinikanth appealed to all. Rajinikanth also had a duet on him. 

Tiger which released amid huge expectations however bombed at the box office due to routine story though Ntr and Rajini combo generated immense hype. This is the only film with Ntr and Rajini in lead.