Lets have some fun with a top 5 list!
First, lets consider core spells only, lets not bring in the expansion books.
Second and very important, we are looking at spells compared to their level. Of course 9th level spells are going to be stronger than 3rd levels ones! But what are the spells that stand out at their level?
Third...lets not look at edge cases where a spell can be cheesed. If a good portion of DMs say "no way I would interpret the spell to allow that", then lets not bother. We want spells that don't need fancy rulings, they are just amazing on their own merits. So no clone army of simulacrums please
Here's my list, in no particular order.
1) Revivify: A 3rd level spell that erases the ultimate condition. No Mid level or higher party should be without it.
2) Bless: A 1st level spell that still packs a punch for 20th level characters. When a 20th level cleric uses their precious concentration slot to cast this spell, and the party cheers instead of looking at them like they are crazy...you know you have a gem on your hands.
3) Counterspell: A 3rd level spell that can completely shut down an enemy caster. Casters with this spell dominate over casters that don't.
4) Wish: There are 9th level spells....and then there's wish. Even ignoring the power of DM fiat this spell can allow....even the examples allowed for this spell are just amazing. Accept no substitute, it is the most powerful spell in the game by a very comfortable margin.
5) Wall of Force: While Forcecage gets all the love for its "automatic binding" of a creature....in most cases wall of force can do the same thing at 2 levels lower. A 5th level spell that can completely shut off a monster (even a legendary one) with no save can never be handled lightly.
So what's your list?
First, lets consider core spells only, lets not bring in the expansion books.
Second and very important, we are looking at spells compared to their level. Of course 9th level spells are going to be stronger than 3rd levels ones! But what are the spells that stand out at their level?
Third...lets not look at edge cases where a spell can be cheesed. If a good portion of DMs say "no way I would interpret the spell to allow that", then lets not bother. We want spells that don't need fancy rulings, they are just amazing on their own merits. So no clone army of simulacrums please

Here's my list, in no particular order.
1) Revivify: A 3rd level spell that erases the ultimate condition. No Mid level or higher party should be without it.
2) Bless: A 1st level spell that still packs a punch for 20th level characters. When a 20th level cleric uses their precious concentration slot to cast this spell, and the party cheers instead of looking at them like they are crazy...you know you have a gem on your hands.
3) Counterspell: A 3rd level spell that can completely shut down an enemy caster. Casters with this spell dominate over casters that don't.
4) Wish: There are 9th level spells....and then there's wish. Even ignoring the power of DM fiat this spell can allow....even the examples allowed for this spell are just amazing. Accept no substitute, it is the most powerful spell in the game by a very comfortable margin.
5) Wall of Force: While Forcecage gets all the love for its "automatic binding" of a creature....in most cases wall of force can do the same thing at 2 levels lower. A 5th level spell that can completely shut off a monster (even a legendary one) with no save can never be handled lightly.
So what's your list?