I'm currently playing my first gigantic game and it's a eye-opener. Generally, I have the game wrapped up by the time I get Dreadnoughts. I moved down a level of difficulty to Tough (only leaving the Yor at Intelligent) and I'm getting a pretty good run for my money. Everyone ended up with 40+ systems except for the Yor who mangaged to grab 4 systems (The Alexians got 3 in comparison and much better systems at that).
Anyway, it's been a lot of fun. Never seen warfare on this scale and the battles seem to last forever. Logistically supporting conquest is a real challenge as well. I've been constantly at war with the Torians and Altarians, in the meantime the Arceans staked out the entire top third of the map. Fortunately, I have a big edge in Population and Influence.
I do have a question for people who play gigantic maps. What is your colonization strategy? I cranked out colony ships early in the game (I actually overproduced them). Since I was cranking them out, new colonies had very little population. I ended up with no edge in number of systems (in fact Arceans and Torians ended up with more, but I had a very hard time with my population which for a while was actually behind the Yors 4 systems). If a had been playing Painful, I would have gotten completely wiped out. Actually, I still needed a lucky break. I invaded a newly founded Torian colony and took Battleship from them by luck (didn't know they had it and it would have taken me 40+ turns to research). Turned around and traded Battleship for Star Democracy and a few others from the Arceans. Arceans and I held Star Democracy to ourselves and my economy / manufacturing picked up to the point where I could hold my own. Traded a ton of techs to the Yor for 5 Starbase resources and a few years later they surrended to me.... otherwise this might have been a loss.
The bottom line is I could use some help on early game stategy at gigantic.