Studying and learning foreign languages has been one of the most rewarding things I've done. I'm very envious of folks who grow up in a situation where they are native speakers of more than one language. I've had to learn foreign languages the hard way, and as my brain has aged, it has definitely become harder.
I have several friends who I never would have gotten to know if I hadn't learned to speak French fluently. I've gone on many trips to French and Spanish-speaking countries with friends who only could speak English, and they were very appreciative of how much easier it was to do some of the things we did, than if I hadn't been on the trip.
I've sometimes found myself participating in some amusing language situations. I once observed a Japanese man and a Frenchman attempting to communicate with each other in English, but neither could understand the other's accent. I ended up "translating" for them.
Years ago, I was staying in a youth hostel in the French Alps and I was perusing my maps at a table. Someone sitting at the table asked me in what sounded like native speaker French, whether I happened to have a guidebook for Switzerland. I told him I did but that it was in English. He said that was OK. I went to get it. We continued speaking in French for a couple of minutes, then he suddenly switched to English, Australian English specifically. The conversation continued but we never asked one another where we were from because we both immediately knew from each other's accent.
Before going to Thailand, I listened to some Thai language tapes to get a feel for the "tones". I brought a phrasebook with me which had Thai phrases transliterated into English. I used the phrase book a few times and got some giggles, but I also got the information I was seeking. It was very satisfying.
As for the rankings of countries by English proficiency, a few of the rankings make no sense to me. I found that it was very easy to travel in Sri Lanka (listed as "Very Low" in English proficiency) as an English speaker. Signs were usually in English, and there was virtually always someone around who could speak English reasonably well.
I'm very impressed with how Singapore has been turned into an English-speaking country, with many kids growing up there now as essentially native speakers.
I'm also impressed with how quickly the study of English has apparently been embraced in the Czech Republic and Slovakia. I was in Czechoslovakia in 1979, and I recall speaking English only twice. I got around by speaking German, as most people who were 40 or older usually knew German well (better than me, typically). Also, at that time, the vast majority of tourists there were from either East or West Germany, and someone told me that employees in hotels and restaurants were required to be able to speak German.