I suppose it is inevitable that a person's favorites will change. Music is a creative pursuit and is thus subject to taste from the POV of the musician and the listener. In this post, I'll take a look at my favorite bands from a few years ago and where I jumped off the proverbial bandwagon. Neither list should be assumed to be comprehensive. There were probably others I could have added to both lists (e.g. Slayer).
Favorites (ca. 2008/2009):
Rush, Tool, Burnt by the Sun, Lamb of God, Mastodon, High on Fire, Meshuggah, Kylesa, Nile, Opeth.
Favorites (2015):
Rush, Tool, Burnt by the Sun, Krallice, Ludicra, Yakuza, VHOL, Inquisition, Immolation.
In some ways, it's harder to say definitively which bands would qualify as "favorites" in 2014. There are certainly some caveats on my list as it stands: Krallice & Ludicra make it with three albums, Yakuza & Inquisition with two, Immolation with two plus an EP, and VHOL with one.
As far as the bands I removed from my favorites between 2008/2009 & 2014:
Lamb of God: Resolution (2012). Seems to signify the end of an era. The progression exhibited through their first four albums stopped with Wrath and Resolution acts as more of a regression than anything else.
Mastodon: The Hunter (2011). The band has changed from metal to pop-leaning rock. Harsh vocals abandoned, as well as most of the heavy riffs.
High on Fire: De Vermis Mysteriis (2012). Similar to Lamb of God, High on Fire previously exhibited progression and this album ends that.
Meshuggah: Koloss (2012). After the triumphant ObZen (2008), Koloss was as much or more of a regression as the previous three bands.
Kylesa: Ultraviolet (2013). To be honest, I was leery of future output after Spiral Shadow (2010), which sounded like a turn toward alt-rock/pop.
Nile: Place taken by Immolation, more or less. I enjoyed At the Gate of Sethu (2012); despite it being a regression in production/presentation, it has one thing that most of the above albums don't, that being riffs.
Opeth: Heritage (2011). I was leery after Watershed (2008), but I couldn't have imagined they'd fall into irrelevance so succinctly.
As far as the bands I added to my favorites between 2008/2009 & 2014:
Krallice: Diotima (2011) and the year of 2011 in general represent a significant increase in the number of bands and number of albums I listen to. Thanks to Diotima, I came to appreciate their 2008 S/T and jumped on the bandwagon for Years Past Matter too. I eagerly await new material.
Ludicra: The Tenant (2010). They may have broken up in 2011, but three of their four LP's (and an EP) represent some of the finest metal the Bay Area has produced (no easy feat, that). I consider The Tenant to be the best metal album of 2010.
Yakuza: Of Seismic Consequence (2010). Not only did this album introduce me to the band, but to Profound Lore Records as an underground metal entity worth following. Yakuza followed with Beyul (2012); I consider both albums to be among the best in their respective years of release.
VHOL: VHOL (2013). Topped my Best of 2013 list. New material forthcoming. Further explanation is unnecessary.
Inquisition: Ominous Doctrines of the Perpetual Mystical Macrocosm (2011). That's a mouthful. And one of the albums that piqued my interest in black metal, despite the fact that 99% of BM sounds nothing like it. Croak away, sir!
Immolation: Harnessing Ruin (2005). As much as I love this album, the next two didn't do much for me. They really became a favorite with Kingdom of Conspiracy (2013), but I was fairly certain that they were onto something with the Providence EP. What do you know, I was right for once.
As far as the bands that hold a place in both lists:
Rush: My favorite band, regardless of genre. Nobody will top what they did from 1975-1984 (with Power Windows and Counterparts as honorable mentions).
Tool: My second favorite band. Although they haven't released anything since 2006 (the less engaging by their standard 10,000 Days), their previous material stands as some of my favorite music that wasn't produced by Rush.
Burnt by the Sun: After a short hiatus from heavy music and a couple of years where I listened predominantly to thrash and nu-metal, Burnt by the Sun was the band to get me into metal. They went out on top with Heart of Darkness. As yet, no other metal band has approximated their style, nor do I expect anyone to do so.