"I love you!" in European Languages
Did you know that the phrase “I love you!” is more commonly used in English than “Good morning!”? (Here’s some proof!). This phrase can be used for lovers or even in platonic or family settings.
Etymology
The origin of the word ‘love’ can be dated back to the Proto-Indo-European word leubh, meaning "care" or "desire". It later evolved into Latin with the word lubet, which went on further to become libet. Libet is also the father of the word libido, which is somewhat connected to love but should be more accurately related to lust. The word then spread to the Germanic language. It then steadily evolved into four forms, each taking the place of the antecedent: lubo, liube, liebe, and then lob, all of which had the modern meaning. These words eventually phased into Old English as lufu, and this word got mangled around until it became love. Many phrases were derived from love, as it was such a powerful and important word in everyday life, including lovebird, lovesick, loveseat, and making love (which originally meant the innocent act of courtship until it became a euphemism and became inappropriate). Today, etymology enthusiasts can be a little surprised that love changed little throughout the history of the words they love. But then again, love loves to love love.
Map
Of course, every language has its own way of expressing love, and the similarities between some of the languages are quite surprising. The colouring scheme of the map is based on etymological relations between the translations of the verb “love”. Relations between other parts of the phrase are not shown on the map.
Notes
Spanish and Italian amo are usually reserved for one’s lover. In the context of friendship or family, quiero and voglio, respectively, would be used instead. Many speakers derive a similar distinction between Ukrainian кохаю (between lovers) and люблю (between any two people), but this may also depend on the dialect and the influence of Polish and Russian languages.
There are a few unusual relations to notice. Most notably, Russian ljublju, German liebe, English love, and similar expressions in many other languages all come from the same Proto-Indo-European root leubh (and hence share the same colour on the map).
Italian voglio and similar verbs in other Italic languages quite surprisingly share a common origin with Croatian volim; they both come from Proto-Indo-Europeanelh (which is also the source of the English word “will”).
Czech miluji and myliu, and mīlu in Baltic languages are likely derived from the same Proto-Balto-Slavic root meilos, although the languages are geographically separated by Polish, which is more closely related to both but where a different expression is predominant (but there is a Polish cognate miłować, which is mostly used in religious and formal contexts rather than everyday speech in modern Polish).

Which version of "I love you" will you use this Valentine's day? I know I will be practising the pronunciation of jag älsker dig like a maniac before the day dawns.
Credit
All credit for the map and some of the information provided here goes to Jakub Marian, who has even more interesting language maps available on his website.