Once considered “too Catholic” for many Protestants to use, today the name Michael has risen to become an extraordinarily popular mainstay on the Top 10 in the U.S. It’s spent many years as #1, most recently in 1998. As of 2015, it was #9. In Ireland, the name was #8 in 2015, and in Northern Ireland (Ireland by any other name), it was #16. Michael has also enjoyed great popularity in Switzerland and Canada.
The spelling Michael is used in English, Hebrew, German, Dutch, and sometimes the Scandinavian languages. Other forms include:
1. Mikhail is Russian, with the familiar nickname Misha. In spite of its current popularity as a woman’s name in the Anglophone world, Misha is a male-only name in the source language. Superdiminutives include Mishenka, Mishulya, Mishechka, Mishutochka, Minyushka, Minochka, and Mishulka. However, superdiminutives should never be used when you don’t know a person very well, even if it’s a child. Grown men also typically aren’t called by superdiminutives by anyone but a romantic partner or someone like a grandparent or mother.
2. Mykhailo is Ukrainian.
3. Mihajlo is Serbian and Croatian.
4. Mihailo is a Serbian-only alternate form. The nickname for both is Mijo.
5. Mihail is Bulgarian, Macedonian, and Romanian. The Romanian nickname is Mihăiță.
6. Michal is Czech and Slovak. The nickname is Míša (pronounced like Misha). This isn’t to be confused with the feminine Hebrew name Michal, which may mean “brook.” The alternate form Michał (MEE-khaw) is Polish.
7. Mihael is Slovenian and Croatian. The Slovenian nickname is Miha, and the Croatian nicknames are Miho and Mijo.
8. Mikhalay is Belarusian.
9. Mikhayla is also Belarusian.
10. Mikhal is a third Belarusian form. The nickname is Mikhalik. The spelling Mikhal is also Ossetian.
11. Mikael is Scandinavian and Finnish. The Finnish nicknames include Mika, Mikko, and Miska.
12. Mikkel is Danish and Norwegian.
13. Miguel is Spanish and Portuguese.
14. Michel is French.
15. Miĥaelo is Esperanto. The nickname is Miĉjo.
16. Mikelo is the modern Esperanto form.
17. Mihails is Latvian.
18. Miķelis is an alternate Latvian form. The nickname is Miks.
19. Mikkjal is Faroese.
20. Mykolas is Lithuanian.
21. Mihály (MEE-hy) is Hungarian. Nicknames include Miksa (MEEK-shah), Miska (MEESH-kah), and Misi (MEE-shee).
22. Mihai is Romanian.
23. Mihkel is Estonian.
24. Mikheil is Georgian. The nickname is Misho.
25. Michail is modern Greek.
26. Michalis is an alternate modern Greek form.
27. Mikha’il is Arabic.
28. Miquel is Catalan.
29. Mikel is Basque.
30. Mitxel is an alternate Basque form.
31. Myghal is Cornish.
32. Mícheál is Irish. The similar form Mìcheal is Scottish.
33. Meical is Welsh.
34. Michiel is Dutch.
35. Mikala is Hawaiian.
36. Michele is Italian.
37. Mikaere is Maori.
38. Mikail is Turkish.
39. Maikeru is Japanese.
40. Mëhill is Albanian.
41. Miceli is Sicilian.
42. Micheli is Sardinian.
43. Michu is Swiss–German.
44. Miqueu is Gascon and Medieval Occitan.
45. Miché is Jèrriais.
46. Michi is an alternate Jèrriais form.
Onomastics Outside the Box 
Michael was a VERY popular name in the USA when I was a kid. I don’t come across many young boys named Michael these days, but little girls named Michaela (and every variant spelling you can think of– Mikayla, Makayla, McKaila) are everywhere.
I think the Michaela trend may have started with Dr. Quinn, Medicine Woman, and then caught on among people who hadn’t watched the show and didn’t necessarily know how the name is traditionally spelled.