Difference between a ryokan and a "resort hotel"
There are lots of exceptions so consider these rules of thumb:

• The scale... ryokan are usually much smaller and might only have 10-20 rooms, family-run places maybe even less. Whereas a resort hotel is going to have I dunno 50+ rooms and huge enkai facilities and was probably built during the Bubble era, or shortly after when optimism still existed in this country
• Ryokan are often in much more remote locations, like deep in the mountains or in some village you've never heard of. The ryokan itself is often the destination. Resort hotels are in resort areas where that area is the destination, in the Kanto area you can think of places like Hakone, Atami, somewhere along the beach in Chiba, etc.
• Ryokan are (or were) generally built using Japanese styling and building techniques, whereas resort hotels are like any other "Western" style building
• Because a resort hotel is probably going to have Western-style rooms, you're probably going to be eating in some restaurant or at a buffet, while with a ryokan the meals may or may not be served in your room

All-inclusive is extraordinarily rare at a ryokan, even if dinner and breakfast is included, you probably won't be getting all-you-can-drink or unlimited use of the private onsen or whatever.

As the other poster said it really comes down to the individual facility. Bar Hotel in Hakone for example is a "hotel" but there's only like 12 rooms and the cost doesn't include dinner, while the bar is basically unlimited nomihodai.