Whether they're the best English club side ever is something that can never be categorically stated, however the point blank refusal of some to acknowledge the fact that they are clearly one of the greatest is utterly baffling. The long term and consistent success of this side is remarkable and, (with no disrespect to the all-conquering Wigan team of the 90's who were operating under a system that made their success easier to come by as opposed to the levelling influence of the salary cap) the only side that can claim to compare is Saint Helens. To pick out Bradford of 2003 or Saints of 2006 is a false argument - brilliance can be fleeting, it can last a season, but greatness is earned over time and only the current Leeds and Saints sides can stake a claim to that.
Since the likes of Sinfield, McGuire, Burrow, Bailey et al first pulled on their shirts they've earned the right to be considered great and for others to argue that they are the greatest ever without being belittled, argued against by all means, but to dismiss this side is myopic and ignorant.
For what it's worth here's what a SL table of the last ten years looks like featuring the current big 4 and Bradford.
Saints 393points 4x1st 3x2nd 2x3rd 1x4th 1x5th 1 Title
Leeds 392points 2x1st 4x2nd 1x3rd 1x4th 2x5th 6 Titles
BIG GAP
Wigan 333points 2x1st 1x2nd 1x3rd 2x4th 2x6th 1x7th 1x8th 1 Title
Wire 315points 1x1st 1x2nd 1x3rd 1x4th 3x6th 1x7th 1x8th 1x10th No titles
Bulls 302points 1x1st 1x2nd 2x3rd 1x4th 1x5th 2x9th 2x10th 2 Titles
The point of all that being that the core of the Leeds and Saints teams over that ten year period of dominance have stayed largely the same and have (as clearly demonstrated) delivered time and time again. That's the mark of greatness. There is no doubt that this Leeds side is great, and to argue that they are not is futile and petty.
The greatest? Each to their own, but it's going to take one hell of a team to eclipse their achievements any time soon and I guarantee you that any team that does will have their fans hailing them as the greatest ever - and surely that's a good benchmark?