The "feeling" of D&D, for me, is pretty general because I tend to think of D&D as the Original trope Fantasy RPG. Other games need to distance itself from D&D, not the other way around. Because of that, I tend to D&D a very large margin of variation. Things that stick out as distinctly D&D are:
• Wizards use Intelligence and spellbooks to ready and cast their spells. Every edition so far as had this feature.
• Fighters are tough, weapon-specializing warriors that excel in combat. AD&D and 4E (and to an extent 5E) did this pretty well while 3E, v3.5, and PF need specific builds to make this true (mostly due to excelling in combat part).
• Clerics are mortal instruments of their deities and channel their divine power in wondrous displays of magics and miracles. Again, every edition so far has had this feature.
• Rogues and Thieves are cunning knaves who use a specific set of weapons and tools for unscrupulous acts. Every edition has met this so far.
• Monsters should include Dragons, Mindflayers, and Beholders.