Barry Richards proved his greatness in the Packer circuit, in SA, in England, in Australia, -at the highest level against all types and qualities of bowlers. Kind of absurd to group him in with the ones you mentioned.
He proved that he was a real talent, yes. Thats all he proved. I tend not to make exceptions to overlook test record when talking about test batsmen. To demonstrate what i mean, he cannot overtake the experience of playing against true pace and spin on subcontinental wickets of that era ( Imran + quality spin or Indian spin quartet), he did not play in Kiwiland, that tends to be batting graveyard for many a great visiting batsman and most importantly, he did not face England either, who did not exactly have a weak attack either. (I'd easily take the attack of Snow-Underwood-Greig-Willis than any 'modern' one of England)
So no, i don't really short-list him for the job.
To put it in perspective, if performances in Australia, vs West Indies ( who Richards also faced in the packer era) , Pakistan (same) and in England were all it took to forge a reputation, in the same era, we have Gavaskar ending all statistical debate to 'who's the best opener ever' by being posting ridiculously huge 'greater than contemporary' figures as 7540 runs @ 55+ average ( that would be a staggering 15% better than his next most successful direct contemporary, ie, another contemporary opener). To put that into context, a 15% gap over your next best rival today, would be the equivalent of Sangakkara ending with a ridiculous 66+ average to move 15% clear of his next best rival, statistically in the average department- Kallis, at the end of their careers.
So to stop rambling, yes, barry had a good case to be considered a very good batsman, one of the finest. But not qualified enough to be in an ATG discussion or 'dream team' of sorts for the test arena, atleast, not for me.
He is a better bat than the hyperboles i used, but that was just to get the point across a bit more, elementally.