Not similar enough IMHO.

How much is "enough" ? Can you measure it ?

Hehe, no I don't think anyone can measure it and other people may have another opinion. To me the similarities here are simple: #1 sportsmen do their sports thing (kick stuff vs throws stuff), #2 airport. Where an ad is set is a bit difficult to use (alone) as a Badland thing, think of how many billion of ads are "family at kitchen table" or "young couples wedding", so the airport alone won't do it. It's not as if the basketballplayers are spending their entire 30 seconds in the ad waiting for a flight and thus erupting in an all-over-theairport impromptu basketball game - which is exactly what goes on in the Nike ad. The Basketballplayers almost do it at the end, but we've seen them jog and brush their teeth and other stuff for the first half of the ad, so I'm kinda thinking... *does that wavy thing with hand* meh, not quite there yet. Close though.

What do other people think?

Like hlebarov says, they're similar. But that's it, nothing more. I'm not sure that the Greek National Basketball team set out to copy the famous Nike ad on purpose here. If they did that's a pretty bad copy. 

I'd weigh in if I could see the ads, but I still can't have flash at work. Please stick to posting Quicktimes here already.

I think the Greek ad is quite obviously inspired by the Nike ad, but a really watered down tame version of it lacking everything that made the Nike ad great. And John Woo.

I'd call it "inspired by"