I know that some people find reggae monotonous and it all sounds the same to them (hello Justine and Jordan!), but really, recommending reggae is like recommending rock and roll. Like, what do you want today, some Chuck Berry, Fleetwood Mac, or Metallica?
There are only a couple of reggae songs on that The Harder They Come album. The rest of the songs are ska from the 60s or ballads. In other words, the reggae equivalent of Chuck Berry and Fleetwood Mac.
Having said that, if you want to know when the golden age of reggae was, I'd say the period of 1973 to 1979/80. If you like sounds that are a little more basic or low-fi, you can go back to 1970. But before that you're getting into ska times. And after 1980 or so synthesizers, samplers, and computers came onto the scene, and those electronic rhythms changed reggae into something else completely, and it's been stuck in that dancehall kind of style ever since.
Anyway, it depends on what you like. But anything recorded in Jamaica in that period of the 70s is a good bet to be at least interesting if not inspirational, motivational, and rootical.
Or, you know, you could start with these mainstream selections available on 8-Track at your local minimart:
The Wailers - Catch a Fire (if you can find the deluxe CD that includes the original Jamaican mix, that's the one to get)
The Wailers - Burnin'
Bob Marley and The Wailers - Natty Dread
Bob Marley and The Wailers - Live at The Roxy
Bob Marley and The Wailers - Survival
Bunny Wailer - Blackheart Man
Bunny Wailer - Struggle
Peter Tosh - Legalize It
Peter Tosh - Equal Rights
Peter Tosh - Bush Doctor
Toots and The Maytals - Funky Kingston
Judy Mowatt - Black Woman
Burning Spear - Marcus Garvey
Burning Spear - Hail H.I.M.
Ras Michael and The Sons of Negus - Rastafari
Ras Michael and The Sons of Negus - Nyahbinghi
Augustus Pablo - Earth Rightful Ruler
Augustus Pablo - East of the River Nile
Augustus Pablo - King Tubbys Meets Rockers Uptown
Hugh Mundell - Africa Must Be Free by 1983
Hugh Mundell - Blackman's Foundation
Mutabaruka - Check It!
Prince Far I - Voice of Thunder
Steel Pulse - Tribute to the Martyrs