Like Idi Amin declaring himself the winner of a general election, so England's return to the top of the ODI rankings should be viewed with a certain cynicism.

While any victory over a decent South Africa side is to be praised, particularly a victory that showed such an improvement on the dismal performance in Southampton, the ranking flatters and misleads. England have a long way to go as an ODI side.

In truth, this ODI series - like so many - is about building for the future. ODI teams are not judged on rankings, particularly ones that appear quite so arbitrary. No, ODI teams are judged on trophies. Global trophies, at that: World Cups and, to a lesser extent, the Champions Trophy. Whatever happens in the next week or so, whichever team wins this series, few will remember by the time the 2015 World Cup comes along.

But England can take encouragement from this performance. As both these teams build for the future, they are developing new players and testing their bench strength. For that reason, a strong argument could be made to suggest that England have the better prospects ahead of next year's Champions Trophy, which is to be played in the UK.

In this game, South Africa looked a batsman light. With Hashim Amla, Graeme Smith and AB de Villiers all, for once, departing to somewhat loose strokes, a thin-looking middle order was exposed. While the jury remains out on Dean Elgar - it is bound to take him some time to settle at international level - Faf du Plessis and Wayne Parnell, at No. 5 and No. 7 respectively, both look at least a place too high in the order.

While many of South Africa's problems would be resolved in a stroke by the return of Jacques Kallis - he strengthens the batting, the bowling and the fielding - he is now 36. Even though he harbours ambitions to play in the 2015 World Cup, South Africa do need to start to look to the future. Replacing him will prove desperately difficult.

"We didn't play good cricket at all," de Villiers said afterwards. "Most of our senior players got in and didn't make it count. Including me. I was seeing it really well, but played a poor shot at a very bad time. It is those things that cost you the game.

"We were about 40 runs short. It was the experienced players at fault. We were hoping for 250 at least and hopefully aim for 270. That would have been a winning score. Complacency wasn't an issue. I wouldn't allow that as a captain. We just didn't play well at all."

The performance of Wayne Parnell, who bowled with controlled pace, should provide some encouragement for South Africa. After a few bumps on the road, the 23-year-old looks to be developing into the top-class performer his talent first suggested.

England, meanwhile, went into this game without three men who might be considered first-choice selections: Stuart Broad, Graeme Swann and Kevin Pietersen. While there is no certainty about the future of any of them, there is growing hope that all should be around in 2013 and 2015. Swann does not require an elbow operation, while Pietersen will meet with ECB officials in the very near future to thrash out their difficulties. A sincere, unqualified apology made face-to-face with colleagues in the squad and the management set-up would take him a long way along the path to rehabilitation. If he really wants to return, it is the option he must take.

"Jonathan Trott may well be the most reassuring batsmen England have had since the retirement of Graham Gooch"

The pleasing thing about this display from an England perspective was that their stand-ins performed so impressively. James Tredwell, bowling with flight and dip that Swann has struggled to find of late, hardly delivered a poor ball, while Jade Dernbach utilised his variations far more judiciously than has sometimes been the case. It hints at a growing maturity. The lovely slower ball, all the more effective for being used sparingly, with which he dismissed Elgar was the delivery of the match.

"We bowled better, we batted better and we fielded better than we did in Southampton," Alastair Cook said. "It's encouraging when we can right wrongs. Swann was fit to play, but it's really nice when you have guys as solid as Tredwell to come into the side."

England's reply was built around two contrasting innings by Jonathan Trott and Eoin Morgan. Trott, all quiet accumulation, and Morgan, full of invention and aggression, complemented each other perfectly and underlined the impression that England are building a team that can adapt and challenge. If Pietersen and Morgan can be reunited in the middle-order, they will prove a potent problem for any bowling attack.

Despite the mountain of evidence to the contrary, some will never accept Trott as a limited-overs batsman. But whatever his perceived issues on the flattest of wickets, there is probably no-one in world cricket who manages the overhauling of a modest target with as much certainty. He may well be the most reassuring batsmen England have had since the retirement of Graham Gooch. Morgan, in this form, looks irrepressible. Quite why he cannot convert such talent to first-class cricket - he averages under 20 in this year's County Championship - is hard to fathom.

"We have guys with various attributes who contribute to different ways of winning a game," Morgan said. "Trotty anchored the innings very well and I played the way I do. It worked out very well. I've worked hard and I've been hitting the ball well all summer."

Perhaps, had Trott played-on off Dale Steyn when he had scored 6, the result may have been different. But there is not a huge amount to choose between these teams and, as both teams look into the longer-term future, perhaps it is England who can be the slightly more optimistic.

George Dobell is a senior correspondent at ESPNcricinfo