Could you define what you mean by "superior" regarding languages ? What is the comparison function ?

The only thing that would make some sense would be the number of people speaking it in the world, but there are more precise words than "superior" to describe that.

What do you mean by superior? That it's used in mainstream applications and has become the standard when it comes to international communication in the west and between the east and the west? English is not superior - it's just more simple (comparatively, especially when you're not striving for grammatical correctness), has fewer fancy characters and has the benefit of being the native language of a country that currently happens to be the most globally dominant superpower in the world. Having a widespread character base also helps, which is only half true for Spanish and not true at all for eg Chinese, Arabic or Indian. Easier (read: less specific) pronunciation (from a personal point of view) goes a long way as well.

This has got nothing to do with one language being superior or another language not being able to fill the same role - it's got everything to do with history and happenstance. Global presence dictates preference - just as Latin used to be the shizzle until a superpower (whose name we no longer speak) took it upon itself to implode on its own arrogance. Or take Babylonian - a cuneiform language that actually came packaged with its own numeric system (base 60, which is still used in geometry et al today). Currently, with 300+ million speakers I wouldn't say Spanish is inferior in any imaginable way. It's just not the language that Hollywood films come and space missions are run in: it's not culturally dominant in the popular circle (click me!). As a side note, consider this.

In 17th-20th century Europe (especially the north and middle regions), English, German and French were almost equal. Russian was hugely affected by French due to warm relations between the two countries' cultural spaces (which happens to exclude the fact that one actually invaded the other). There literally was no linguistic preference before the first world war when the US began to tip the balance on a global scale, and the scientific circles remained multilingual for decades to come.

Hawaiian - now there's a language that I would consider inferior purely from a linguistic point of view. In pretty much any other sense I'm not sure I understand your question.

I think it would best be answered by a non-native english or spanish speaker.

My take on english is that there's no gender which is nice, and conjugation of verbs is quite easy. In English, you only need to know one conjugation for each tense because the pronoun forms the verb, in spanish you have to know five conjugations for each tense.

Probably the coolest thing about English is that there are relatively few dialects that are unintelligible. An Indian, Australian, Englishman, and a Canadian can all talk to eachother and understand eachother pretty well. Contrast that to something like Hindi where you can be down the street talking the same language and not understand the person. Though spanish probably falls in the same category as well.

Spanish is nice because it's completely phoenetic. Spelling and reading are all pretty easy. If there is a word with an irregular pronunciation, it is shown with an accent mark.

My guess is that spanish would be easier to learn to read and write, and that english would be easier to learn to speak. I would not want to be a non-native and have to try to spell in english though, that would suck.