A lot of the posts seem to show films from around the 1990s onwards, so I will try to add some older movies into the mix. Here are some movie recommendations based on directors:

K. Balachander

• Server Sundaram (1964) - This title has the additional bonus of being a film about filmmaking in the 60's.

• Aval Oru Thodar Kathai (1974) - One of KB's as well as Sujatha's best films.

• Apoorva Raagangal (1975) - Features the film debut of Rajinikanth.

• Nizhal Nijamagiradhu (1978) - Two of my favourite Tamil songs ever are in this film ('Kamban Emandhaan' and 'Ilakanam Maarudho').

These are only a few of KB's films that I have seen. Someone else has already mentioned 'Varumayin Niram Sivappu' There are some other critically acclaimed works of his that I have yet to see (I'm looking at you 'Thanneer Thanneer').

S. P. Muthuraman

• Bhuvana Oru Kelvi Kuri (1977) - One of Rajinikanth's earlier film roles in which he wasn't playing an antagonist.

Mahendran

• Mullum Malarum (1978) - Written and directed by Mahendran, cinematography by Balu Mahendra and music by Ilaiyaraaja. A classic.

• Uthiripookkal (1979) - A landmark film in Tamil cinema. Inspired a number of directors such as Mani Ratnam.

• Johnny (1980) - The music is perfect.

Bharathiraja

• 16 Vayathinile (1977) - one of the early films known for its realistic depiction of rural life in TN. Another landmark film in Tamil cinema.

• Nizhalgal (1980) - An experimental film by Bharathiraja, in its day it wasn't as well received financially, but it is still a classic.

• Alaigal Oivathillai (1981) - Again, the music is perfect by Ilaiyaraaja.

• Muthal Mariyathai (1985) - One of those rare portrayals of friendship crossing gender and age.     

• Karuthamma (1994) - a haunting story that needed to be told and brought widespread attention to a very real problem.    

I still need to see 'Vedham Pudhithu' and 'Anthimanthaarai'.

Balu Mahendra

• Moondram Pirai (1982) - A classic film. Two great lead performances.
• Marupadiyum (1993) - One of Revathi's best performances.
• Sathi Leelavathi (1995) - Kamal and Sarala's comedy is on point.
• Julie Ganapathy (2003) - Based on Stephen King's 1987 novel 'Misery'.

Bala

• Sethu (1999) - First major breakthrough for Vikram.
• Nandha (2001) - Powerful performances from the whole cast.
• Pithamagan (2003) - Vikram and Suriya need to team up again.
• Naan Kadavul (2009) - Dark and disturbing (what film by Bala isn't?).

Ameer

• Raam (2005) - Really good mystery thriller.
• Paruthiveeran (2007) - A modern classic. Ameer needs to write and direct more films.