I think variety (large leaf basil?) and amount of light has a lot to do with the size of the leaves.

Way too many plants for that size pot. Basil needs 8-12" spacing between plants (though I personally do two plants together). In a pot one basil needs 8" pot. However, they're usually sold in groupings that are way too thick. Thinning them will lead to larger plants, as crowded basils will stay smaller, with smaller leaves.

But, even on a healthy plant, the leaves only get as large as the varietal. Some are bred for larger leaves, but a traditional basil does have small to mid size. If you want really large leaves, go for something like a lettuce leaf basil.

Thanks so definitely a larger pot then?

Yup, and thin that one down to 1 plant.

Depending on what you want to invest, I have really good luck with basil in an Earthbox if you stick with containers. I do 8 plants per box, and consistently they grow 2-3 ft tall, and quite bushy with harvesting. Even this year, when my weather has been so screwy, my earthbox is full as ever, when the inground basil didn't even top 1 ft.

wow sounds awesome!! do you have a pic you wanna share? how big is a box? 8 plants in 1 box sounds like a lot for 1 earth box. Thanks again for the feedback..

Sorry, I can't take a pic since it was harvested today due to expected frost and/or snow. The earthboxes are nice sized--their instructions say 6 herb plants per box, but I have done 8 every year with the annuals. My perennial box I do keep to 6. With basil, you have to make sure they have water--sometimes twice a day in major heat with that many plants. You'd have to check the earthbox website for specific size--they hold 2cu ft of soil. Spendy to start with, but mine have been used for 8yrs now and are still in great shape. And that's with all outdoor storage.