No one has claimed that post 2000, he has been the batsman he was in the 90s. But neither was Richards later in his career - and did much worse than Tendulkar in fact.
For the last 7-8 years though?
This is a difficult one. For Tendulkar's average to have dropped to 46 this century (hardly horrible though), when so many talk about rubbish attacks this century, how easy pitches are now, bats have come on in power, ropes are in, outfields are like lightning, bowlers only have one leg, fielders only throw under arm and drop catches at will and generally nothing after 1 January 2001 is any good about the game at all, means he may well have been in decline for a while.
By the same token, he's played so much cricket for so long that until I read this thread I hadn't realised his average this decade had dropped to that extent, and he's still a joy to watch imo.
Viv certainly had a sharp decline in his later years, but I don't think you can say that because he had such a strong line up he could bat how he wanted, whereas Tendulkar couldn't. Whether you've got Lloyd, Richardson, Haynes and Greenidge or not, if a fella's bowling to you at 90 mph or if he's spinning it square, you've still got to be good to dominate - and both these guys have in their own eras. Indeed, India's strength in the middle order for the last several years (Ganguly, Dravid, Laxman, then the advent of Dhoni) seems to have coincided with the slide in his average.
I wouldn't put the bowling of the 70s and 80s all that far behind that in the 90s either. I'd concede the 90s was a stronger decade, but not by a massive margin. Pakistan had Imran and Sarfraz, England had Botham and Willis, Australia (for part of the time) had Lillee, then McDermott, Lawson et al, NZ had Hadlee, India Kapil and some really good spinners too. Of course, there was no SA at all for Viv to compare, and when they came back they were pretty good from ball one. Then again, Viv didn't get a crack at the Zimbobs or the Bangers, so when he played he was nearly always up against established test sides.
I would also suggest that one mght wish to factor in the relative pitches. Richards' home pitches in the 70s and 80s had more in them than Sachin's home decks in the 90s and 00s.
Really, both are master batsmen, but their mastery is expressed differently. Richards was not averse to playing in a non-text book fashion, and while Tendulkar can do the same, I don't think I've ever seen a bat which looks wider when it plays straight than his. Tendulkar is a more compact player, and perhaps becasue of this his attacks don't look as savage as those of Richards, or indeed others like Botham and Gilchrist. Still, watch how quickly the ball races over the ground when Tendulkar goes hard. There's not that much between them really.
I've seen both play a fair bit, and stylistic issues aside, I really find it very, very difficult to split them at all.
Despite having splinters in my arse from sitting on the fence on this one, it's where I'm gonna stay. Too hard.