If the marriage was arranged then it's not a surprise that you wonder what else is out there, it's human nature to be curious. Unfortunately this is something you would have to weigh up the pros and cons - imagine getting what you want, this amazing sex life with a man you describe as your physical ideal... then what?
Do you ultimately value having a best friend for a husband more than a great sex life? There are many articles about why sex lifes can get dull in long term relationships and marriage... if you have never felt attracted to him in that way, then 1. kudos for the long marriage 2. you, and he, deserve to be with someone you ARE attracted to... You must love someone for more than their looks, but you must feel attracted and drawn to them.
If you once did, and no longer are attracted, it seems as though you need to communicate your needs and desires, speak to him about his and figure out why that lust has disappeared... Unfortunately again though, it sounds as though your issue won't be fixed by some whips or a kinky spontaneous roll outside.
Life is too short, not to feel excited about your life, friends, job and partner - and to love what you have at least most of the time. If you don't feel content with what you have and you're in a constant state of what if, the only way to move forward is speak to your husband about maybe having a 3-some to cure it, take a break/split completely... but it's all up to what you value most.
At the end of the day, it isn't fair on either of you to be in a relationship like you described.