The only other language that can have a similarly credible case for learning it would be Mandarin, but unlike Spanish, that's only good for one country. For anyone living in the Sinosphere, that would obviously be the best choice, but for someone living in the US, Chinese isn't nearly as important. Plus, Spanish is way easier to learn, given that it shares an alphabet, similar pronunciation, and through casual exposure you likely already have a start on a basic vocabulary.
As for Arabic ... yeah, that's far down the list. I've only ever been to one Arabic country (the UAE), and more people there speak English than Arabic. Obviously that's atypical for Arabic countries, but way more westerners are likely to go the UAE than to, say, Egypt.