Which poem follows the terms and requirements of an elegy better, Lycidas or "Elegy Written in a Country Churchyard"?

The essential characteristics of the elegy, which are:

1. invoke the Muse


2. express the shepherd's (or poet's) grief


3. praise the dead


4. inveigh against death


5. tell the affects of death on a personified nature


6. accept death and acknowledge a hope of immortality

are missing or modified in Thomas Gray's elegy "Elegy Written in a Country Churchyard," while they are all present inMilton's Lycidas.

In the first place, in Gray's there is no invocation of the Muse. On the other hand, Milton does so invoke the Muses in Line 15 in Lycidas. Gray doesn't directly express a shepherd's or the speaker's grief at the death spoken of, and Gray is speaking of many deaths, the deaths of all in the churchyard. Milton does express the grief of the shepherd lamenting Lycidas' death.

Both poets praise the one being lamented.
Likewise, both inveigh against (protest against) death. Gray's is mild in Stanza's 5 and 6, while Milton's is more pronounced in Lines 50 through 63:

"Where were ye Nymphs when the remorseless deep [ 50 ]
Clos'd o're the head of your lov'd Lycidas?"

Both lament the effects on nature of the lamented ones' deaths. Gray says: "How bow'd the woods beneath their sturdy stroke!"
Milton says:

"And all their echoes mourn.
The Willows, and the Hazle Copses green,
Shall now no more be seen,
Fanning their joyous Leaves to thy soft layes."

Gray ends with what the speaker hopes will be his epithet at his own death, which accepts death and expresses hope in Christian immortality. Milton likewise fulfills this characteristic. In Gray's elegy, the speaker reposes in "The bosom of his Father and his God," while Milton says of Lycidas, "In the blest  Kingdoms meek of joy and love./ There entertain him all the Saints above."

In conclusion, Milton's Lycidas appears to have the correct structure as it pertains to the elegiac form. Gray's elegy is highly innovative as it laments many dead, doesn't have a shepherd speaker and in the end turns out to be an anticipatory lament of his own death. Incidentally, in Lines 19 through 24 of Lycidas Milton's speaker hopes some Muse will sing a lament to his death as he is singing Lycidas' death.