They had friendship power, but they didn't know how to use it. The message being a guild like saber tooth that only cares about results does not foster the strength that a guild like fairy tail which supports its family does. Natsu was fighting for Lucy in a way that Sting couldn't really match.
But thats the whole issue, Sting was actualy fighting for what was proberly his oldest and best friend, Natsu was just fighting for his desire for vengeance, by all that we have seen so far in the serie Sting should have won that fight.

this. On the other hand, Sting and rogue were 2 overhyped little b*tches. One could argue that by leaving for 7 years FT's main cast has left a powervacuüm. If they are gone long enough the bar for great power may have been lowered. Besides, Sting and rogue weren't using the power of friendship, they were using the curse of arrogance. They were fighting like they 'only' needed to push Natsu and Gajeel in the dirt so they could prove they were superior, while Natsu and Gajeel actually had a bone to pick with ST. For instance about harrassing Lucy, and the other Celestial wizard they exiled from their guild. Besides, with the way DS magic powerrating works, despair is a limiter, determination and vengeance are accellerators.
Yeah, well if the author had been able to manage a consistent system of power then they would also be deserving of the hype, what with being able to enter DF at will and all

And Sting certainly had the greater claim for the power of friendship, seing as he was not fighting for himself, but for what was proberly his oldest and closest friend.
Natsu meanwhile cant really claim anything but a desire for revenge thats quite misguidet, seing as neither Rogue nor Sting has ever laid a hand upon another member of FT (besides Gajeel).

with all the animosity between Natsu and ST, see above, besides, Natsu has a powerlevel over 9000, especially since he got his reserves doubled and migrated into not only fire, but lightning as well... that scanner is right you know...
Yes, see the mentioning of ruining above, now that Natsu has shown he is able to take both of them down at once without going serious, then its allmost impossible to take what could have been some great recurring antagonists seriously.

again, ayup, you guessed it, emotions+DS magic=win (it's becoming a pattern isn't it? Almost sees like Naruto's Sharingan hax)
And thats another problem with the abuse of the emotionally boost DS magic can pull out, as before the timeskip it was only providing a minor boost.

The Natsu i grew to love won though determination and from friends assisting him, this new post-timeskip DBZ rubbish is something you can keep, i dont want any of it.

Lucy getting beaten didn't do it for me. Oh lucy needs to lose... But she has the best chances with having the key to aquarius and all. No worries, Aquarius will go into bitchmode leaving Lucy powerless.

elfman was awesome all right. he fought like a Real Man(tm)
Tbh, the only thing i found stupid in the Lucy fight was the way she lost, Celestrial magic has generally turned out quite useless in my eyes, but when the summons cant even be bothered to assist her it becomes close to worthless.
The Elfman fight however was awesome, proberly the best fight in the arc.