To help remind you of many great musicals of the past here's Channel 4(UK) list of "100 greatest musicals" which was aired a few years back(and highly entertaining). Don't let the positions influence you.
1. Grease (1978)
2. The Sound of Music (1965)
3. The Wizard of Oz (1939)
4. West Side Story (1961)
5. Mary Poppins (1964)
6. Singin' in the Rain (1952)
7. The Rocky Horror Picture Show (1975)
8. Chicago (2002)
9. Oliver! (1968)
10. Moulin Rouge (2001)
11. Chitty Chitty Bang Bang (1968)
12. My Fair Lady (1964)
13. Buffy the Vampire Slayer (1992)
14. The Lion King (1994)
15. Les Misérables (1998)
16. Willy Wonka & the Chocolate Factory (1971)
17. Cabaret (1972)
18. Joseph and the Amazing Technicolor Dreamcoat (1999)
19. Bugsy Malone (1976)
20. The Phantom of the Opera (2004)
21. Little Shop of Horrors (1986)
22. Evita (1996)
23. The King and I (1956)
24. The Blues Brothers (1980)
25. Calamity Jane (1953)
26. Annie (1982)
27. The Jungle Book (1967)
28. Jesus Christ Superstar (1973)
29. Fame (1980)
30. Cats Don't Dance (1997)
31. Blood Brothers (1993)
32. Seven Brides for Seven Brothers (1954)
33. Fiddler on the Roof (1971)
34. High Society (1956)
35. Oklahoma! (1955)
36. Guys and Dolls (1955)
37. White Christmas (1954)
38. The Nightmare Before Christmas (1993)
39. South Pacific (1958)
40. 8 Mile (2002)
41. Carousel (1956)
42. Starlight Express 3D (2003)
43. Snow White and the Seven Dwarfs (1937)
44. Tommy (1975)
45. A Star Is Born (1954)
46. A Chorus Line (1985)
47. Summer Holiday (1963)
48. Gentlemen Prefer Blondes (1953)
49. The Muppets Take Manhattan (1984)
50. Hello, Dolly! (1969)
51. Thoroughly Modern Millie (1967)
52. Carmen Jones (1954)
53. Cinderella (1950)
54. On the Town (1949)
55. Hair (1979)
56. Meet Me in St. Louis (1944)
57. Paint Your Wagon (1969)
58. An American in Paris (1951)
59. Funny Girl (1968)
60. Top Hat (1935)
61. Scrooge (1970)
62. Sweet Charity (1969)
63. Jailhouse Rock (1957)
64. Easter Parade (1948)
65. The Jazz Singer (1927)
66. Gypsy (1962)
67. Doctor Dolittle (1967)
68. Kiss Me Kate (1953)
69. The Producers (1968)
70. Gigi (1958)
71. Show Boat (1951)
72. Godspell: A Musical Based on the Gospel Acco... (1973)
73. Half a Sixpence (1967)
74. Shall We Dance (1937)
75. Dil Se.. (1998)
76. Dancer in the Dark (2000)
77. Porgy and Bess (1959)
78. Hedwig and the Angry Inch (2001)
79. All That Jazz (1979)
80. Sweeney Todd: The Demon Barber of Fleet Stre... (2007)
81. Yankee Doodle Dandy (1942)
82. Anything Goes (1956)
83. A Star Is Born (1976)
84. Ziegfeld Follies (1945)
85. Funny Face (1957)
86. There's No Business Like Show Business (1954)
87. Million Dollar Mermaid (1952)
88. For Me and My Gal (1942)
89. A Little Night Music (1977)
90. Cry-Baby (1990)
91. Everyone Says I Love You (1996)
92. The Umbrellas of Cherbourg (1964)
93. How to Succeed in Business Without Really Tr... (1967)
94. Sholay (1975)
95. Breaking Glass (1980)
96. Lullaby of Broadway (1951)
97. The Cotton Club (1984)
98. Bright Eyes (1934)
99. The Heat Is On (1989)
100. Let's Make Love (1960)
More than likely A Star Is Born (2013) is gonna become my all time fave.
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1. Dreamgirls
2. Grease
3. Little Shop Of Horrors (ironically Ive been playing this soundtrack just this week)
4. Fame
5. Annie
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Now those are my favorite musicals, but my favorite songs from musicals are way different.
- Ladies Who Lunch
- Don't Rain On My Parade
- Sweet Transvestite
- Listen
- And I Am Telling You
- Skid Row (Downtown)
- Out Here On My Own
- There Are Worse Things I Could Do
Cell Block Tango >>>>>>>>>>> 
Buffy, Fiddler, and My Fair Lady are definitely my top 3 though.
But in no specific order:
).