This spell list was selected with the thought that damage dealing spells get bonus consideration.
1. Delayed Blast Fireball: Hands down the best damage dealer in the game in the hands of a well spec'd caster. The spell can even be used situationally in epic play. Not a good performer though for the DC challenged or inexperienced casters.
2. Polar Ray: This spell does not take the top spot since it is only a single target ray spell. However, its lack of a save and wide range of performance make it a top performer.
3. Mass Hold Monster: One of the most useful spells in epic play. This spell does not need to be heightened to perform at full capacity. A well spec'd caster can neutralize more foes than the melee can deal with even in epic play.
4. Frost Lance: This spell makes the top of the list because of its great potential damage output. In today's multiple TR DDO world, even WF casters can get their evocation focus to pretty high levels. For the well spec'd caster this spell will put out near as much damage to foes at 11th level as a polar ray at 20th. A well spec'd capped sorc can multi cast with this spell and polar ray in quest (like the Shroud) and essentially double DPS by firing the equivalent of two polar rays back to back.
5. Charm monster/Mass Charm monster and Suggestions: These spells would rate higher on the list if they had some epic play use. Unfortunately charms fell to the wims of the designers (which indicates how tough charming mobs really is). Charms are a combination of CC and Attack spell since the mobs fight each other. In the hands of a well spec'd caster, charm will last longer than suggestion, so in my opinion is a better choice.
6. Finger of Death / Wail of the Banshee: Another spell whose potential was cut dead by the "Its easier to nerf than think of a way to balance its performance" approach used by the designers. Outside of epic play and red named foes this spell(s) can dominate play in the hands of a well spec'd caster. Just bump your DC past 40 and you will find out.
7. Invisibility / Mass Invisibility: This spell is often scroll cast but still is an outstanding performer. It can make many aspects of the caster's life much easier. Areas include, solo play zerging, party wipe stone collecting, first attack setup, and many other uses.
8. Otto's Sphere of Dancing: This very versatile spell was reborn with the level advancement to 20. In epic play and regular questing there is probably no better CC. It's many benefits include the need for mobs to make saves every time they enter; its relatively short casting time; its quick cooldown; and its ability to knock off 15 points!!!! on the DC of reflex saves.
9. Disintigrate: This red headed step child of a spell often gets overlooked. However, it can be a very high damage producer in the hands of a well spec'd knowledable caster.
10. Fire ball / Acid Blast: These low level AOE spells dominate the game 6th thru 12th level for knowledgeable well spec'd casters.
11. Niacs Cold Ray: The best damage spell for knowledgeable well spec'd casters level 1-5, in the hands of a good caster can see extended life thru 12th level of play. A niac's/acid blast combination can really pump out the damage.
12. Cone of Cold: Only the 15 die damage max keeps this spell out of the top 5. This spell in combination with polar ray in the hands of a well spec'd caster will make mobs melt away in Shavarath.
13. Force missile: A good damage producer, this spell in combination with a spell like polar ray will help a caster put out the most DPS of anyone against very high save foes. It's also useful to deal with hyper immune mobs.
14. Ball Lightning: The 15 point maximum damage and the acid/electric enhancement line keeps this reflex save spell out of the top 5.
15. Scorching Ray: Another good spell for the DC challenged. This spell is also situationally very good against fire sensitive foes like frost giants.
16. Otto's irresistible dance: A favorite of WF casters and those DC challenged foes. This spell also has uses in epic play by all.
17. Web: Casters new to their art love this spell. It can be used to quickly lock down foes. However, its short duration and sensitivity to fire and some acid spells keeps it out of the top 10. It also has good performance in epic play.
18. Eagles Splendor: This spell makes the top 20 due to its incredible value to a caster in the first half of his life. Since this spell is available in many forms, there is no excuse not to have a +4 bonus to charisma prior to 10th level for any sorcerer.
19. Enervation / Level Drain: A well spec'd caster rarely needs to resort to these spells anymore, otherwise they might have ranked higher. However, my WF still has at least one hot keyed.
20. Jump: This spell is so naturally necessary to the performance of a good caster that it was almost overlooked.
21. Expeditious retreat: A great spell at all levels of play. Haste need never be taken or an item slot never used to increase the speed of your caster.
22 Wall of Fire: Favorite of melee, wizards, and novice sorcerer alike. This spell is situationally very useful. For example, any time you find yourself low on mana. It probably would not make the list if not for its necessity in epic play.
23. Ghoul touch: A little used very nice necro schooled spell. It can be used in many levels of epic play
24. Glitter dust: Another little used spell. This spells just screws with the performance of the AI. In addition to acting as a good CC, it essentially is a quick and dirty way to give the whole party displacement in an engagement. It even works against undead.
25. Halt undead: The best way to lock down those pesky epic undead casters. The spell will help make any undead run (epic or not) a cake walk.
Good spells not making the list: Resist energy, protection from energy, knock, haste, teleport, Ooze puppet, Greater heroism, trap the soul, and displacement just to name a few.