Yeah, I'm still thinking there is too many subgenres but I have to admit I'm not a death metal fan really I just like a few bands, I'm really picky about metal. Probably cause I'm a rock, blues, jass guy at heart.Genres are good, makes it easier to find bands I will like, and avoid bands I won't. So, since I don't like metalcore, I can avoid bands like Trivium, Unearth, and As I Lay Dying, while looking for death metal bands like Suffocation or Morbid Angel.
In Flames, Arch Enemy, etc are what is commonly referred to as "melodic death metal", or melo-death. Other bands of this type would be At The Gates, Soilwork, The Absence, Scar Symmetry, etc.
Personally, I prefer the older death metal, like Obituary, Death, Cancer, Disincarnate, Immolation, Malevolent Creation, etc. Some newer stuff is great as well, like Nile.