I am a big Starcraft fan but I have never been into online play (because I suck at it). I played the original SCII beta a few times online and lost all but one match because it was another new player and I did a cheap zerg rush so I could feel like a winner.
I think that, despite my experience, there is a fairly large amount of people you can find who play non-competitively. It is something I have been thinking about getting in to but I honestly have never tried, I personally like fighting AI opponents because when I lose to them (which I do), I know that no one is mocking how shit I am at a game that I have played far too much to be so bad at.
TBH, having played Wings of Liberty and Heart of the Swarm exclusively for the singleplayer, I honestly felt I got my money's worth. The campaigns for both games are a dozen or so hours long (very dependent on difficulty settings and player skill) and they have pretty good replayability. You get to customize some things that are irreversible in each playthrough, heavily altering the usage/value of some units and this means playing through the campaign twice with different upgrades makes missions work very differently. Plus there are (a few) missions where you have to make a decision that affects some things, so you can play through again to get more plot.
That said, if you are really in to the story of the series like I am, I would consider waiting until Legacy of the Void comes out before getting Heart of the Swarm. Heart of the Swarm has a cliff-hanger-ish ending while Wings of Liberty's ending felt like it designed in the event that they never made Heart of the Swarm. And ultimately, regardless of whether or not Legacy has a conclusive ending, I personally was resistant to playing Heart of the Swarm multiple times because they always ended in a cliffhanger.
Also, I have no idea how Heart of the Swarm affects the multiplayer experience, I only tried multiplayer a few times on the beta and I think only once after wings of liberty came out, so I have no idea about which game to get if you only want multiplayer.
Also, the mod community is pretty awesome for Starcraft 2, especially if you like the multiplayer aspect. I hope Legacy of the Void's hero mode leads to some more singleplayer mods though.
Final also: Starcraft 2's single player has a difficulty selector, so the issue of the game becoming impossible like Brood War isn't a concern (AND YES THE FINAL FEW LEVELS OF BROOD WAR WERE IMPOSSIBLE, I WILL NOT HEAR ANY ARGUMENTS CONTRARY)
I think that, despite my experience, there is a fairly large amount of people you can find who play non-competitively. It is something I have been thinking about getting in to but I honestly have never tried, I personally like fighting AI opponents because when I lose to them (which I do), I know that no one is mocking how shit I am at a game that I have played far too much to be so bad at.
TBH, having played Wings of Liberty and Heart of the Swarm exclusively for the singleplayer, I honestly felt I got my money's worth. The campaigns for both games are a dozen or so hours long (very dependent on difficulty settings and player skill) and they have pretty good replayability. You get to customize some things that are irreversible in each playthrough, heavily altering the usage/value of some units and this means playing through the campaign twice with different upgrades makes missions work very differently. Plus there are (a few) missions where you have to make a decision that affects some things, so you can play through again to get more plot.
That said, if you are really in to the story of the series like I am, I would consider waiting until Legacy of the Void comes out before getting Heart of the Swarm. Heart of the Swarm has a cliff-hanger-ish ending while Wings of Liberty's ending felt like it designed in the event that they never made Heart of the Swarm. And ultimately, regardless of whether or not Legacy has a conclusive ending, I personally was resistant to playing Heart of the Swarm multiple times because they always ended in a cliffhanger.
Also, I have no idea how Heart of the Swarm affects the multiplayer experience, I only tried multiplayer a few times on the beta and I think only once after wings of liberty came out, so I have no idea about which game to get if you only want multiplayer.
Also, the mod community is pretty awesome for Starcraft 2, especially if you like the multiplayer aspect. I hope Legacy of the Void's hero mode leads to some more singleplayer mods though.
Final also: Starcraft 2's single player has a difficulty selector, so the issue of the game becoming impossible like Brood War isn't a concern (AND YES THE FINAL FEW LEVELS OF BROOD WAR WERE IMPOSSIBLE, I WILL NOT HEAR ANY ARGUMENTS CONTRARY)