The world of DOS is very huge and deep. Discussions of it's games and applications can go on for years. No, seriously!
I think the best way too experience these classics is self discovery. Head over to MobyGames and browse through the respective sections. You can browse the different categories including the year of release. Each of us like different games a lot, in spite of having similar ones at the same time.
Some of us still like PC versions of Dig-Dug, Alleycats, Tapper, Zaxxon, Lode Runner, Asteroids, etc.
Wargames were aplenty by SSI amongst others. SSI (Strategic Simulation Inc.) was also known for releasing numerous well liked Advanced Dungeon & Dragon RPG games.
Microprose used to release some realistic Simulations after Simulations - F-15 Strike Eagle series, Stealth Fighter series, Silent Service submarine series, Gunship chopper series, etc.
Of course, Sierra On-Line with their classic Quest games - King's Quest, Space Quest, Police Quest, Quest for Glory and Leisure Suit Larry series.
And Gods, Lemmings, Civilization, Colonization, the Original Simcity, Syndicate, System Shock, Ultima series, and Prince of Persia and Karateka and .....soooooooooooooooooooooooooooo many of them.....!!
And these are just 4 or 5% of the total DOS games. Haven't touched Windows 3.x and Win95 based software. And haven't touched the thousands of sharewares too!
As for other software, and applications like productivity suites, system tools and utilities (apps is a "new" term after the advent of smartphones), it totally depends on what you want to do.
So, as SquallStrife said Fried Green Tomatoes, it can be anything.