The allmusic list is much shorter with just one or two picks from several of their writers. They're a lot more interesting picks than the DigitalDreamDoor list, but the DigitialDreamDoor list is a lot more interesting from the point of view of actually ranking the very best epic songs. I started trying to make my own list, and I found I needed to break it out into categories.
Category #1: Classics. These are songs from the 60s and 70s that I would have picked for the top of a list like the DigitalDreamDoor list.
30) Working Man - Rush (1974, 7:11)
29) Eagle - ABBA (1978, 5:53)
28) Sparkle City - Shuggie Otis (1974, 5:58)
27) Fire On High - Electric Light Orchestra (1975, 5:32)
26) Radar Love - Golden Earring (1973, 6:27)
25) Beginnings - Chicago (1969, 7:51)
24) It's A Rainy Day, Sunshine Girl - Faust (1972, 7:25)
23) Children Of The Sun - Billy Thorpe (1979, 6:45)
22) Celluloid Heroes - Kinks (1972, 6:23)
21) Paradise By The Dashboard Light - Meat Loaf (1977, 8:29)
20) No Agreement - Fela Kuti (1977, 7:52)
19) Baker Street - Gerry Rafferty (1978, 6:01)
18) War Pigs/Luke's Wall - Black Sabbath (1970, 7:58)
17) Interstellar Overdrive - Pink Floyd (1968, 9:41)
16) Come Sail Away - Styx (1977, 6:07)
15) American Pie - Don McLean (1971, 8:37)
14) Hold Your Head Up - Argent (1972, 6:15)
13) Beautiful As The Moon - Terrible As An Army With Banners - Henry Cow (1975, 7:02)
12) Aqualung - Jethro Tull (1971, 6:37)
11) Free Bird - Lynyrd Skynyrd (1973, 9:10)
10) Kashmir - Led Zeppelin (1975, 8:29)
9) A Day In The Life - The Beatles (1967, 5:34)
8) You Can't Always Get What You Want - Rolling Stones (1969, 7:33)
7) Band On The Run - Wings (1973, 5:10)
6) Roundabout - Yes (1972, 8:32)
5) Jungleland - Bruce Springsteen (1975, 9:33)
4) Nights In White Satin - The Moody Blues (1967, 7:30)
3) The End - The Doors (1967, 11:44)
2) Shine On You Crazy Diamond (Parts I-V) - Pink Floyd (1975, 13:40)
1) Alice's Restaurant Massacre - Arlo Guthrie (1967, 18:37)
29) Eagle - ABBA (1978, 5:53)
28) Sparkle City - Shuggie Otis (1974, 5:58)
27) Fire On High - Electric Light Orchestra (1975, 5:32)
26) Radar Love - Golden Earring (1973, 6:27)
25) Beginnings - Chicago (1969, 7:51)
24) It's A Rainy Day, Sunshine Girl - Faust (1972, 7:25)
23) Children Of The Sun - Billy Thorpe (1979, 6:45)
22) Celluloid Heroes - Kinks (1972, 6:23)
21) Paradise By The Dashboard Light - Meat Loaf (1977, 8:29)
20) No Agreement - Fela Kuti (1977, 7:52)
19) Baker Street - Gerry Rafferty (1978, 6:01)
18) War Pigs/Luke's Wall - Black Sabbath (1970, 7:58)
17) Interstellar Overdrive - Pink Floyd (1968, 9:41)
16) Come Sail Away - Styx (1977, 6:07)
15) American Pie - Don McLean (1971, 8:37)
14) Hold Your Head Up - Argent (1972, 6:15)
13) Beautiful As The Moon - Terrible As An Army With Banners - Henry Cow (1975, 7:02)
12) Aqualung - Jethro Tull (1971, 6:37)
11) Free Bird - Lynyrd Skynyrd (1973, 9:10)
10) Kashmir - Led Zeppelin (1975, 8:29)
9) A Day In The Life - The Beatles (1967, 5:34)
8) You Can't Always Get What You Want - Rolling Stones (1969, 7:33)
7) Band On The Run - Wings (1973, 5:10)
6) Roundabout - Yes (1972, 8:32)
5) Jungleland - Bruce Springsteen (1975, 9:33)
4) Nights In White Satin - The Moody Blues (1967, 7:30)
3) The End - The Doors (1967, 11:44)
2) Shine On You Crazy Diamond (Parts I-V) - Pink Floyd (1975, 13:40)
1) Alice's Restaurant Massacre - Arlo Guthrie (1967, 18:37)
Category #2: Punk era through the 1980s.
25) Chichen-Itza Elvis - Copernicus (1987, 7:53)
24) I'm Considering a Move to Memphis - Colorblind James Experience (1987, 6:42)
23) All White People Look Alike - Brian Woodbury (1987, 20:38)
22) How I Learned to Love the Bomb - Television Personalities (1985, 5:07)
21) Tokyo Storm Warning - Elvis Costello & The Attractions (1986, 6:25)
20) Dreams of Sexual Perfection - Fugs (1986, 11:52)
19) Rock And Roll Dreams Come Through - Jim Steinman (1981, 6:27)
18) Sister Europe - Psychedelic Furs (1980, 5:39)
17) How Soon Is Now? - Smiths (1984, 6:46)
16) Two Tribes - Frankie Goes to Hollywood (1984, 7:59)
15) Sweat Loaf - Butthole Surfers (1987, 6:09)
14) Teen Age Riot - Sonic Youth (1988, 6:58)
13) Rock Lobster - The B-52's (1979, 6:51)
12) People Who Died - Jim Carroll Band (1980, 5:00)
11) Porn Wars - Frank Zappa (1985, 12:05)
10) High In a Flat - The Bevis Frond (1988, 7:49)
9) O Superman - Laurie Anderson (1982, 8:25)
8) Marquee Moon - Television (1977, 10:40)
7) Sex Bomb - Flipper (1982, 7:49)
6) Teen Love - No Trend (1984, 7:41)
5) I Believe - Buzzcocks (1979, 7:08)
4) 30 Seconds Over Tokyo - Pere Ubu (1975, 6:25)
3) The Days Of Wine And Roses - The Dream Syndicate (1982, 7:33)
2) Gloria - Patti Smith (1975, 5:55)
1) Bela Lugosi's Dead - Bauhaus (1982, 9:36)
Category #3: The 1990s through the present. I don't know how well this list holds up against the other two. It's the one that needs the most revision.
25) The Frequency - Jets To Brazil (2002, 6:15)
24) Die Arden En Die Mens - Blomkrag (2003, 6:40)
23) Glover - The Aliens (2007, 8:23)
22) L. Frank Baum - Bags (1991, 5:53)
21) We Want War - These New Puritans (2010, 7:23)
20) Two Beautiful Beaches - B-Sides (2001, 5:43)
19) The Good, The Bad And The Queen - The Good, the Bad & the Quee n(2007, 7:00)
18) No Place - Eskimo (1990, 6:10)
17) Emma Blowgun's Last Stand - Beulah (1999, 5:22)
16) Age Of Adz - Sufjan Stevens (2010, 8:00)
15) Home - Edward Sharpe & The Magnetic Zeros (2009, 5:03)
14) I Would Hurt A Fly - Built To Spill (1997, 6:15)
13) Don't Know When But A Day Is Gonna Come - Bright Eyes (2002, 6:32)
12) I Made a Date (With An Open Vein) - Trembling Bells & Bonnie 'Prince' Billy (2012, 6:34)
11) Ballad Of The Sin Eater - Ted Leo/Pharmacists (2003, 5:20)
10) Inner Meet Me - Beta Band (1997, 6:20)
9) Whiskey & Speed - Josh Fix (2007, 6:21)
8) Pride approaching - Elope (2003, 6:44)
7) One Nail Draws Another - Utotem (1991, 14:58)
6) Wake Up - Arcade Fire (2004, 5:35)
5) Accused of Stealing - The Delgados (2000, 5:42)
4) Lesson 6: The Lecture - Jurassic 5 (1997, 6:35)
3) The Next Messiah - Jenny Lewis (2008, 8:45)
2) Moby Octopad - Yo La Tengo (1997, 5:49)
1) Folk Song - Bongwater (1990, 9:24)
I didn't have any strict definition of "epic", but I did require that all songs on these lists be at least 5 minutes long. Songs with multiple movements and twists and turns definitely got bonus "epic" points, and some very long very good songs didn't make the list just because.