It's sad that most of the problems Gaye sings about on this album are just as relevant as they were when he recorded it, if not more so. A masterpiece.  This is what makes it truly timeless. You can play this in the 1800s and have the themes be relavent. You can play this 100 years from now and it will be relavent. If any album captures the human condition better than"What's Going On" I would sure love to hear it. Not to mention it's huge impact. He gave Motown artist creative freedom. Imagine not only the Marvin albums after this we wouldn't have gotten, but the great Stevie Wonder classics such as "Songs In The Key Of Life" for example. What is really great about this album for me is it doesn't just bring up a bunch of problems and not resolve them, it offers the most obvious and simple solution: to love. The amazing thing is people as a whole will never learn that. That's why this album will always will be relavent. If there is a god, Marvin was his messanger with this album.
This album will never stop being important, the messages in these songs will always need hearing. Musically and sonically this album sounds as fresh as it was when it came out over 40 years ago. This album is easily the greatest thing that Motown brought into the world, when they brought meaning and a powerful message into popular music.
Music that heals, and brings you up when you are feeling down... it moves you from within, in an intelligent and compassionate manner, acknowledging your pain and offers the subtle relief that only a man who felt the pain himself could...
His best album. Lyrically it's remained relevant and musically it's very cohesive (arguably his most well strung together album, track by track). Another note is that it boasted three very successful singles, all having to do with social consciousness (which isn't as easy as making love songs - the subject matter of later albums such as Let's Get It On and I Want You). I'd be willing to put "What's Going On", "Mercy Mercy Me", and "Inner City Blues" against any other trio songs by Marvin on any other album of his.
My mum lived in Italy in a US army base when this album was released and her brother was like 'WOAH, what is this?'... outstanding music, changing the world. No one can dislike this album if you have love for music.