Microgaming's The Gaming Club claims to be the oldest online casino, but I don't think it is. Others from that period include Intercasino(Cryptologic), Casino-On-Net, casinos powered by Starnet (World Gaming) and Galaxiworld. Boss Media looked like a strong contender to thrive, I wonder why they didn't.
Early cheapo providers were Gambling Software, Handa Lopez, Iglobal, IQ Ludorum.
There are a couple that never took off even earlier. Of operators, Golden Palace has been around a long time.
Early entrants into the industry had fewer troubles than they do now; and those they had were of their own making, such as being hosted in Canada or the US (Starnet); giving away huge bonuses and then stiffing players (Golden Palace); running rigged software (Handa Lopez, Iglobal); being crooks (Galaxiworld); having crap software; going cheap on credit card security services and getting lots of chargebacks and fraud.
The industry as a whole shot itself in the foot by mistreating the credit card companies--credit cards werre never designed as player *payment* instruments, so the payments were processed as merchant refunds. Which means that the credit card companies were also refunding their fees to players. The gambling sector also had a record fraud rate, which is a lot of work for the credit card companies, to do transactions then rescind them etc.