There is a sloka which says about these mahakavis:
उपमा कालिदासस्य भारवेरर्थगौरवम्
दन्डिनः पदलालित्यं माघे सन्ति त्रयो गुणाः
Upamaa kaalidaasasya bharaverarthagauravam
Dandinah padalaalityam maaghe santi trayo gunaah
Kalidasa excels in the use of similes and metaphors in his poetry, Bharavi’s works are pregnant with meaning, Dandi’s language is simple and lilting and poet Magha combines in him all the three qualities mentioned above
By this and by the comments expressed by others, Bharathiyaar qualifies as Mahakavi (according to me)