There are no such thing as the best ad format for all advertisers. The ad format you choose will depend on your goals, product type, budget, and many other factors.
As a general rule, Shopping ads are the best for ecommerce websites selling physical products. Children’s games for example. But note, that this niche is very competitive, using placement targeted image ads could be also a good option. Of course, if you have “large inventory” as in given question, Shopping ads will be much easier to set up.
If you’re a retailer, you can use Shopping campaigns to promote your online and local inventory, boost traffic to your website or local store, and find better qualified leads.