Ganguly didn't feature at all during India's 4-0 thrashing in South Africa in November and December last year, having earlier been stripped of the captaincy following clashes with then coach Greg Chappell.
But the left-handed batsman was back by the time of the World Cup, making 66 in the shock five-wicket first round defeat by Bangladesh at Port-of-Spain in March that, combined with a loss to Sri Lanka, saw India exit the tournament.
Ganguly, 34, is set to take his place at the top of the order for Friday's second one-day international against South Africa, a match India must win to prevent the Proteas gaining an unbeatable 2-0 lead in the three-match series.
"I personally think Sourav Ganguly in the squad gives a huge amount back to India," said Arthur.
"Sourav still has a presence, I think he's a quality player and it still mystifies me how he wasn't in the squad in South Africa," added Arthur of a batsman who in 293 one-day internationals has scored 10,838 runs at an average of just under 42 with 22 hundreds.
"I think he seems to have given a steely resilience back to India."
India captain Rahul Dravid was quick to stress that Ganguly was being treated like anyone else. "He does bring experience into the side. But at the end of the day you've got to get runs and take wickets. Each and every member of our team is equally valuable.
"Sourav does bring a lot of experience and knowledge," added Dravid of Ganguly, who made 73 not out in India's nine-wicket win against Ireland on Saturday but 13 in Tuesday's four-wicket defeat by South Africa.
"He's played a lot in these conditions and on these type of wickets, so hopefully he'll fire in the next couple of games."
Jacques Kallis, captaining South Africa while Graeme Smith recovers from knee surgery, is definitely 'firing' after his 91 not out guided the Proteas to victory in Tuesday's series opener.
But Arthur said it was time for South Africa's other batsmen to ease the burden on the all-rounder.
"I've challenged our batters. I want to see one of our other top five do what Jacques did.
"Jacques's been brilliant and he's done it for years for us, and he will continue to do it for years, which is the good thing. I'd like to see a couple of our other batters come through.
"If you look at our top five, they are all very young. AB de Villiers, he's still a youngster finding his way and Morne van Wyk is here pretty much as a stand-in for Graeme.
"Herschelle Gibbs has done it for a long period and Hersch has given us a lot of innings of substance of late, especially at the World Cup, and then we are looking at blooding a youngster at five in JP Duminy. You want them to glean from the experience of Kallis.
"That knock the other day was class, it was really a fantastic innings."
The series concludes at Stormont on Sunday.