The best replacement for bigcommerce is shopify.

The best alternatives to bigcommerce are rated as following:
★★★★★  shopify
★★★★★  volusion
★★★★  magento
★★  3dcart
★★  woocommerce
★★  corecommerce
★★  squarespace
★★  magento go
★  americommerce
★  prostores
  pinnacle cart
  yahoo store
  godaddy
  amazon webstore
  interspire
  bigcartel

Your alternative for bigcommerce is not listed? Suggest!
Speaking about bigcommerce, one probably shouldn't forget about quickbooks.

Other search terms related to bigcommerce and their ratings are:
★★★★★ quickbooks
You have in mind a companion for bigcommerce and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of bigcommerce in all years. Click on graph for more.
bigcommerce
shopify
volusion