I think so, if for levelled spell we understand spells of level 1+. According to the Magic Item:
The ring can store up to 5 levels worth of spells at a time. [...]
Any creature can cast a spell of level 1 through 5 into the ring by touching the ring as the spell is cast. [...]
While wearing this ring, you can cast any spell stored in it. The spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster but is otherwise treated as if you cast the spell. [...]
Are spells cast from a Ring of Spell Storing considered leveled spells?
I think so, if for levelled spell we understand spells of level 1+. According to the Magic Item:
Yeah; it stores a spell as it was cast, so you can upcast into it and it's stored at that level.