I usually play one elite army and one mob army so that I don't get stuck in a rut and can enjoy both styles of gameplay.
For me this is Dark Elves and Orcs both in fantasy and 40k.
That said, I can definitely see the appeal of other armies. For myself I nearly started as Ogres instead of Orcs for fantasy (and now I get both woohoo!).
Vampire counts are also a bit of a draw card for me, partly because of the awesome Dracula style fluff and partly because I feel that the last Vamp update was when GW really lifted their game model wise.
I do understand your massive army woes although I doubt I have as many models on the table at one time as you.
As I collect 2 armies for each game my models are more split between the two factions so the issues are not so much as massive amount of greenskins so much as it's just a massive amount of models.
You can still use your current models for the game by the way. I sure intend to.
For me the reason to play this game is that you like playing it.
It's a hobby.
I have a certain amount of money each pay which I allocate to spend on my hobby.
Now I might spend that going to the movies with a friend or have a guys night or something.
Or I can spend it on plastic, glue and paint.
If I was into a sport I might spend my "allowance" on that instead.
Basically this is my fun money and I can and do spend it on the things that make life fun for me.
Sadly this probably makes me an ideal sucker for GW as I don't try to justify my expenditures!