Before Battlefleet Gothic, Games Workshop released Space Fleet in 1991.  It came with 4 plastic ships to build, 2 Imperial and 2 Eldar.  The lid of the box also was used for rolling the dice and was divided into 9 squares and where the dice stopped would determine if the attack hit or not.
GW followed up with articles in multiple White Dwarf magazine issues covering the background of the game a great deal of additional rules and stats and information on the line of metal miniatures that were produced by Citadel.  The articles were in issues 139, 140, 141, 146, 147 of White Dwarf.
The miniatures were quite interesting and the Imperial Fleet grew quite large with many new minis but also some of the support ships were actually re-used miniatures from QT Models whose ships had been aquired by Citadel like several of the miniatures in Citadel's Space Cruisers and C43 and C44 lines.
The Eldar fleet only got 2 ships, the metal version of the Wraithship, plastic ship in the box and a smaller Shadowhunter.
The Tyranid Hive Fleet defined in White Dwarf 146 was quite extensive and did feature several ships that had been part of Citadel's Space Cruiser line in the past.

Gothic Imperial Fleet

Background The original Space Fleet box includea a couple plastic Gothic Battleships  When the metal miniatures were released it included an updated Gothic Battleship that had some minor differences.  Additional miniatures with the same asthetic were released including a smaller battleship, a cruiser, and destoyer.  I have included these as a Gothic subfleet to separate them from the rest of the Imperial ships Design Philosophy Hull strength is average.  Screens are prevalent except for the old IRONCLAD class that has armour.  Mainly beam batteries with offsetting arcs and a Pulse Torpedo foreword.

 

COBRA class Destroyer Mass 16 Cost 54/41 Average Hull 4 (1/1/1/1) Thrust 6 FTL 1 Fire Control 1 PDS 1 Class 1 Beam Battery 1 Short Range Pulse Torpedo (F)
FIRESTORM class Light Cruiser Mass 40 Cost 138/114 Average Hull 12 (3/3/3/3) Thrust 4 FTL 2 Fire Controls 2 PDSs Level 1 Screens 1 Class 1 Beam Battery 2 Class 2 Beam Batteries (F/FP/AP, F/FS/AS) 1 Pulse Torpedo (F)
IRONCLAD class Battleship (Heavy Cruiser) Mass 77 Cost 259/241 Strong Hull 28 (7/7/7/7) Armour 7 points Thrust 2 FTL 2 Fire Controls 3 PDSs 3 Class 1 Beam Batteries 6 Class 2 Beam Batteries (3xF/FP/AP, 3xF/FS/AS) 3 Short Range Pulse Torpedoes (3xF)
GOTHIC class Battleship Mass 95 Cost 335/330 Average Hull 28 (7/7/7/7) Thrust 2 FTL 3 Fire Controls 4 PDSs Level 2 Screens 2 Class 1 Beam Batteries 4 Class 2 Beam Batteries (2xF/FP/AP, 2xF/FS/AS) 2 Class 3 Beam Batteries (F/FP/AP, F/FS/AS) 2 Pulse Torpedoes (2xF)
GOTHIC class Battleship (Modified) Mass 112 Cost 399/412 Average Hull 32 (8/8/8/8) Thrust 2 FTL 3 Fire Controls 1 ADFC 6 PDSs Level 2 Screens 2 Class 1 Beam Batteries 6 Class 2 Beam Batteries (2xF/FP/AP, 2xF/FS/AS, 2xAll Arcs) 2 Class 3 Beam Batteries (F/FP/AP, F/FS/AS) 2 Pulse Torpedoes (2xF)   The plastic version of the GOTHIC Battleship that came with the original version of Space Fleet is a bit longer and has extra detail in the front neck area of the mini.  Thus it should be a modified command version of the GOTHIC Battleship