From stardot.org.uk: the highest score from each round, up to 2017-11-29:
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Season 1: 2013-7-1 - 2013-12-2:
S1 R1  Bug blaster:         86117  'leenew'
S1 R2  Chuckie Egg:        574370  'MatthewThompson'
S1 R3  Frenzy:          1,204,981  'sydney'
S1 R4  Guardian:          374,500  'TopBanana'
S1 R5  Rubble Trouble:     24,802  'JoolsH'
S1 R6  Starship command:    2,180  'fibble'
S1 R7  Despatch rider:     21,305  'ivor_the_injun'
S1 R8  Mr. EE:            361,550  'M_Ron'
S1 R9  Galaforce:          54,620  'ivor_the_injun'
S1 R10 Duck!:             130,800  'steve3000'
S1 RC  Snapper (V2):      163,540  'M_Ron'


Season 2: 2014-1-6 - 2014-6-9:
S2 R1  Airlift:           123,780  'ivor_the_injun'
S2 R2  Space pilot:       328,300  'The Kraken'
S2 R3  Tapper:            390,150  'JoolsH'
S2 R4  Moonraider:        306,500  'JoolsH'
S2 R5  Swoop:               6,310  'ivor_the_injun'
S2 R6  Frogger:            14,030  'ivor_the_injun'
S2 R7  Skirmish:          176,300  'ivor_the_injun'
S2 R8  Planetoid:         416,425  'TopBanana'
S2 R9  Felix meets the evil weevils
                           47,600  'Ivor_the_Injun'
S2 R10 Overdrive          151,540  'JoolsH'
S2 RC  Arena 3000:         52,149  'Steve3000'


Season 3: 2014-6-16 - 2014-11-17:
S3 R1  Starship command:    3,150  'chrisn'
S3 R2  Spaceman Sid:        3,200  'MatthewThompson'
S3 R3  Yie Ar Kung fu:    496,700  'ivor_the_injun'
S3 R4  Pengo:              84,530  'MatthewThompson'
S3 R5  Deathstar:         271,700  'KarateEd'
S3 R6  Astro plumber:      20,600  'KarateEd'
S3 R7  Android attack:    194,675  'JoolsH'
S3 R8  Space hi-way:      103,775  'sydney'
S3 R9  Anarchy zone:       27,060  'KarateEd'
S3 R10 Carnivale:          45,780  'tricky'
S3 RC  Ghouls:              3,442  'JoolsH'


Season 4: 2014-11-17 - 2015-5-11:
S4 R1  Spectapede:        185,650  'JoolsH'
S4 R2  Bird strike:        67,560  'KarateEd'
S4 R3  Astroblaster:       32,150  'tricky'
S4 R4  Whoopsy:           162,150  'JoolsH'
S4 R5  Licence to kill:    98,030  'JoolsH'
S4 R6  Firetrack:         703,120  'tricky'
S4 R7  Thrust:            108,900  'chrisn'
S4 R8  Arcadians:          17,700  'TopBanana'
S4 R9  Monsters:           21,170  'chrisn'
S4 R10 Cylon attack:       54,480  'JoolsH'
S4 RC  Hard hat harry:    125,840  'JoolsH'


Season 5: 2015-6-1 - 2015-11-2:
S5 R1  Meteors:            27,650  'TopBanana'
S5 R2  Crazee rider:       58,190  'JoolsH'
S5 R3  The maze:            3,286  'MatthewThompson'
S5 R4  Blast!:              3,549  'KarateEd'
S5 R5  Lode runner:       322,450  'KarateEd'
S5 R6  Killer gorilla:     86,900  'chrisn'
S5 R7  Ransack!:           80,150  'MatthewThompson'
S5 R8  Lemming syndrome:    3,310  'JoolsH'
S5 R9  Barbarian:           2,500  'KarateEd'
S5 R10 Galaforce:          34,180  'Fwibbler'
S5 RC  Fortress:           35,600  'KarateEd'


Christmas crackers!: 2015-11-30 - 2016-1-11:
Christmas crackers! (2015)  Castle of gems:      8,200  'chrisn'
Christmas crackers! (2015)  Duck!:              95,600  'steve3000'
Christmas crackers! (2015)  Hopper:             25,776  'JoolsH'
Christmas crackers! (2015)  Santas Delivery:     2,730  'MatthewThompson'
Christmas crackers! (2015)  Frenzy:          1,059,095  'sydney'
Christmas crackers! (2015)  Qwak:                2,610  'steve3000'


Season 6: 2016-10-3 - 2017-3-6:
S6 R1  Zenon:              42,050  'JoolsH'
S6 R2  Cybertron mission:  57,070  'chrisn'
S6 R3  Mouse trap:          7,720  'Tom_Lindberg'
S6 R4  Mr. Ee!:           136,200  'JoolsH'
S6 R5  Stryker's run:      21,500  'chrisn'
S6 R6  Android attack:    243,360  'JoolsH'
S6 R7  Frogger [tricky]:   51,120  'Tom_Lindberg'
S6 R8  Tapper (beginner)  955,725  'JoolsH'
S6 R9  Arcadians:          19,050  'JoolsH'
S6 R10 Tetris:              8,579  'JeremyGrayson'
S6 RC  Nightmare maze:     13,500  'FourthStone'


Season 7: 2017-3-6 - 2017-8-7:
S7 R1  Banana man:         91,810  'MatthewThompson'
S7 R2  Hunchback:           5,510  'FourthStone'
S7 R3  Galactic firebird:  39,550  'sydney'
S7 R4  Estra:              88,270  'chrisn'
S7 R5  Zalaga:            250,770  'FourthStone'
S7 R6  Vindaloo:          370,470  'JoolsH'
S7 R7  Video's revenge:    99,680  'JeremyGrayson'
S7 R8  Repton:            130,805  'MatthewThompson'
S7 R9  Blast!:              3,779  'KarateEd'
S7 R10 Galaforce 2:       359,060  'Wouter Scholten'
S7 RC  Rocket raid:        64,660  'Wouter Scholten'


Season 8: 2017-9-4 - 2017-?-?:
S8 R1  A maze in space    120,600  'KarateEd'
S8 R2  Manic miner         27,310  'Barbarossa69'
S8 R3  Star wars          391,906  'chrisn'
S8 R4  Caveman capers      11,255  'KarateEd'
S8 R5  Cosmic camouflage    6,075  'Jeremy Grayson'
S8 R6  Felix meets the evil weevils
                           29,300  'JoolsH'
S8 R7  Bumble bee               ?  '?'
S8 R8  Pipemania                ?  '?'

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Unlimited time frame scores, starting from 2016-1-25, as of 2017-11-15:
Fortress:                  81,350  'Wouter Scholten'
Mr. Ee!:                  205,200  'MatthewThompson'
Boulderdash:                6,873  'MatthewThompson'
Plan B2:                   17,955  'sydney'
Warehouse:                  4,260  'sydney'
Drain mania:               16,150  'ChrisB'
Hunkydori (Bugbyte)        27,700  'KarateEd'
Nevryon:                    7,810  'MatthewThompson'
Chuckie egg:              493,140  'MatthewThompson'
Guardian:                 471,150  'Wouter Scholten'
Planetoid:                979,450  'Wouter Scholten'