I have all of SC and Warcraft franchise. Warcraft II was horrible, don't buy that (if it even exists anymore). Warcraft III and its expansion are a pretty good game, and share many similarities with Starcraft II. They are strategy games with several 'races' to choose from. Each race has their own pros and cons. The games bring a single player and multi player mode, with warcraft's being the longest of the two (significantly, SC2 campaign lasted me 3 days).
The main feature about these games are their multiplayer options, having custom maps and playing against people, teaming up etc. If you are into these games for this option, I would recommend you get SC2 as it's a much newer game and has a much wider user base to play with/against, as WC3 has quite some years now and might not be as active as it once was.
In a nutshell, both games require strategic play with a race of your choice, and are mostly played online. They are fantasy as well, so it has little to do with Age of Empires, although they are based on the same concepts.
I'm guessing you play in diamond league within every ladder then?