One thing that hasn't been mentioned is quality of the ingredients. Do the tomatoes have a decent taste when eaten fresh? How about the canned variety (sauce or whole)? If that is lacking to begin with, trying to jazz it up with other stuff isn't going to help a whole deal.

I'm not sure what growing conditions are out like in the Pampas but you might try growing your own tomatoes. They are a lot tastier than the store-bought stuff especially since you can pick them when they're ripe (unlike stuff that is picked green for transport and allowed to change colour (or sometimes forced to by gas) - these never develop a good flavour.)

As for pizza sauce, that is generally a plain tomato sauce (with herbs such as oregano/marjoram, maybe basil and thyme) reduced until it is thick.

If you're looking for variety, I can tell you a whole bunch of ways to make pasta more exciting but I think one of them has been ruled out (only four ingredients: spaghetti, olive oil, black pepper and anchovies).