Value wise, only Subban and Price are in Ovechkin's league.
Team wise, I'm not sure I'd swap Gallagher for Ovechkin. Seriously. Ovy has shown nothing but signs of decline while not showing much, if any, leadership qualities and is now barely useful (to not say a detriment) to his team for everything, except for the power-play. Do I want that on my team for 10M a year for the next 6 years? He's 28 now, will be 34 by then. Ovechkin's decline has been quick and steady over the last 4 years. Do the math.
I sense some kind of Alexei Yashin type of career ending for Ovechkin. Unless some major changes happen, both in his work ethic and his commitment to the game, I don't see what's all that attractive going for that sort of trade. As cliché as it may sound, Gallagher is a heart and soul type of player that gives it all every shift, loved by the fans and teammates, can already pot 20 a season, could pot near 30 in his prime... That's the kind of player I want on my team. Plus, he's cheap, and young. I don't see him resigning for a more expensive deal than Pacioretty, which bodes very well for us.
Again, from a market value perspective, it would be stupid to decline, but I think there's more that come into play than just that. I'm fine building around Price and Subban. Pacioretty fills the sniper winger role just fine.