There are 2 ways to look at this; technical and personal. They tend to intertwine, however.
Technical:
First, we should define early solid state pinballs as machines from 1977 - 1984.
Next, we can look at pinside's own top 100 (comprised of 1000s of pinhead's detailed rankings). Here are their top machines as of 5/22/2019:
1) Fathom #45
2) Centaur #58
3) Eight Ball Deluxe #65
4) Star Gazer #73
5) Barracora #75
6) Flash Gordon #76
7) Seawitch #88
Quicksilver #89
9) Spirit #92
10) Medusa #96
11) Black Hole #100
12) Firepower #102
13) Paragon #104
14) Catacomb #107
15) Joker Poker #115
16) Space Shuttle #125
17) Gorgar #130
18) Centaur II #133
19) Black Knight #137
20) Xenon #138
21) Frontier #139
22) Skateball #142
23) Haunted House #143
24) Stars #145
25) Laser Cue #149
26) Nine Ball #150
While there may be a few outliers, this list in the top 150 should pretty well represent the best machines of the early ss era.
We can cut out some of the similar layouts and styles like nine ball, haunted house, joker poker, and centaur II.
This is where it gets tough. Things like price, artwork, and availability become very important. Fathom, centaur, star gazer, and quicksilver are all expensive these days. There is some great artwork in this era (the best imo), but that leaves games like skateball and laser cue behind.
This leaves Flash Gordon, EBD, barracora, and seawitch at the top.
For me, it is tough to beat the quality, price, artwork, and gameplay of ebd and flash gordon.