If you want to get really into it, search for and read Kenji Lopez-Alt's posts on SeriousEats.com for messing with chili. Great stuff.
That said, the best chili I ever made was a vegan chili that I made and then added some browned ground beef to. As far as I can recall, that recipe was:
diced onion and garlic cooked down,
cooked brown lentils that were blended up (to thicken it),
a can each of black, light-red kidney, regular kidney, and cannelini (white kidney) beans.
canned diced peppers (anaheims, cubanelles, whatever),
a diced jalapeno,
a chipotle pepper with adobo sauce,
your usual spices (cumin especially),
a can of beer (cheap beer's fine, IMO, though it kinda smells like cheap beer when you're done, even though it doesn't necessarily taste that way).
a can of hominy, which is nixtamalized corn and is delicious - think marbles of corn tortilla and that's close enough.
some diced tomatoes, but not tons.
some marmite, which gives it a bit of umami since there's no meat (yet). You can use fish sauce or sardines or any other umami-heavy addition you want (I've used straight-up MSG 'flavor enhancer/salt replacement' before).
So yeah, you basically mix that all together after you cook the onions and garlic, and you get a very nice vegetarian chili (could be vegan depending on if you use fish sauce or not, etc...). And like I said, adding some shreddar cheese and/or beef to it really brought it over the top to be the best chili I've had. It's not necessarily a simple/quick one, but it is damn good, and scales/freezes well.
That said, I don't always want that kind of chili. Sometimes I want something that's just meat, peppers, and spices. Sometimes it's for green or white chicken chili, which is delicious too. Back in college I would cut up a steak (housemate's dad worked in a slaughter house and sent these terrible frozen sirloins) and brown it up, then deglaze the pan with a shot of jack daniels, and then lay in cumin, onion powder, garlic powder, and chili powder and mix in a bit of water to make it a sauce. I'd put that on top of spaghetti, with some shreddar cheese, and that was delicious too, if not technically chili.