English is without a doubt the actual universal language. It is the world's second largest native language, the official language in 70 countries, and English-speaking countries are responsible for about 40% of world's total GNP.
English can be at least understood almost everywhere among scholars and educated people, as it is the world media language, and the language of cinema, TV, pop music and the computer world. All over the planet people know many English words, their pronunciation and meaning.
The causes for this universality are very well known and understandable. English first began to spread during the 16th century with British Empire and was strongly reinforced in 20th by USA world domination in economic, political and military aspects and by the huge influence of American movies.
The concept of a Universal Language is more significant only now, in the era of world mass communication. Before this era Greek, Latin, French were to some extent universal languages, though mainly in Europe.
By a lucky coincidence due to factors above, English, the Universal language, is one of the simplest and easiest natural languages in the world. The only other simple and easy languages are constructed ones.
Of course the concept of easiness is relative, and it depends on which language you know already. However the concept of simplicity is undeniable: English in an easy language to learn, understand and speak. A complex language such as Hungarian would be a very unlikely candidate for a universal language.
First of all, English Language uses Latin alphabet, the most universal, simple and short one (only the Greek alphabet is shorter and simpler). In addition, in English, the Latin Alphabet presents its most "clean" form as a true alphabet with only 26 basic letters and no diacritics;
Verb conjugation is very simple and easy. Even for irregular verbs, there is almost no variation in person (except 3rd singular in present tense).
Regular verbs have only four forms: Infinitive + Present, Past Tense + Past Participle, 3rd person singular Present Indicative, Present Participle.
There are almost no Inflections. No number or gender inflection for adjectives, articles, adverbs. For adjectives there is only comparative and superlative, almost only number for nouns. In pronouns there are gender and number inflections and only three declension cases (Acc/Dat, Nom, Gen).
English is one of the most analytical languages, with no significant synthetic, fusional or agglutinative characteristics.
Could be there any other alternative for Universal Language, instead of English?
There are other languages that are quite simple and synthetic, with almost no verb conjugation, no declension, such as Asian languages like Thai and Chinese, but they are written with complicated scripts and are tonal languages. However if Chinese were to be written with the Latin alphabet, it could potentially become a univeral language.
There are other strong languages that, due to population and economic power, could be univeral languages, but they have a number of disadvantages when compared with English.
Japanese: has very regular verbs but also a very complicated script.
Chinese: no conjugations or declension, but a very complicated script and tones.
German has many more inflections than English.
The major Romance languages, such as French, Spanish and Portuguese, have fewer inflections than most of languages, but their verb conjugation is very complicated.
Russian has both complex verb conjugations and numerous noun declensions.
In conclusion, it is lucky for us that our universal language is the simplest and easiest, even though that simplicity and easiness weren't the reasons that lead English to that condition.