I'd love to jump in with a suggestion of a game that would hook you in right from the start, keep you busy for months, and leave you so grateful to me for suggesting it that you're eternally grateful and never forget my birthday, but as it happens all the best RTS games I can think of you've already played or have already been suggested here. So all I can do is repeat a few of them to emphasise how much you should play them, and add a few more, lesser games to the list:
Starcraft (plus Starcraft: Brood War)
Get over the fact that it's old and just play it. Despite being an RTS fan since Dune II (1992) I only played Starcraft last year and loved every minute of it. The graphics aren't that bad and the gameplay is rock solid. Plus Starcraft 2 will be ready 'when it's ready' according to Blizzard, and it continues the story, so you've got time and a reason to play Starcraft and Starcraft: Brood War first.
Warcraft (all of them, well, maybe just II and III)
The Warcraft series is excellent - you should at least play Warcraft III plus its expansion, The Frozen Throne. I played those upon release and only recently went back to play the older games. The first one is a bit frustrating to play due to its primitive control system (click one unit, click move, click where you want it to move to, click the next unit... basically no option to drag select) but if you have the patience, you can get through it. Warcraft II is a huge improvement and highly recommended.
Warhammer 40,000 - Dawn of War (plus all the expansions, plus DoW2)
Yeah, it kind of is just Company of Heroes with a Warhammer 40k theme, but that makes it more of the same, where 'the same' is a good thing, and you can't have too much of a good thing. Also, you're an RTS fan who's played a lot of RTSs and is looking for more, so Dawn of War is a perfect answer.
Supreme Commander (plus Forged Alliance, plus SC2)
You said Total Annihilation was good for the time, well Supreme Commander is Total Annihilation for modern times as its the spiritual successor.
Rise of Legends
You said you loved Rise of Nations, so have you tried this?
Dune series (Dune II, Dune 2000, Emperor - Battle for Dune)
Before Command & Conquer, Westwood Studios made Dune II. They later remade it as Dune 2000 and created a sequel, Emperor, around the time of Red Alert 2. All are worth playing, Emperor especially.
Homeworld (plus Cataclysm and Homeworld 2)
Despite their age, these are excellent space-based RTS. Of course, if you want something along these lines but more recent there's always:
Sins of a Solar Empire (plus Entrenchment and Diplomacy)
An awesome, and incredibly detailed, series of space RTSs. You can get the game bundled with the expansion packs as 'Sins of a Solar Empire: Trinity'.
Star Wars - Empire at War (plus Forces of Corruption)
A Star Wars RTS...
Warhammer - Battle March (plus Mark of Chaos)
An RTS with a classic (medieval) Warhammer style.
Perimeter (plus Emperor's Testament and 2: New Earth)
A RTS that was praised for innovation when it was released, due to its unique terraforming and base defense aspects.
If I think of any more I'll be back...
Starcraft (plus Starcraft: Brood War)
Get over the fact that it's old and just play it. Despite being an RTS fan since Dune II (1992) I only played Starcraft last year and loved every minute of it. The graphics aren't that bad and the gameplay is rock solid. Plus Starcraft 2 will be ready 'when it's ready' according to Blizzard, and it continues the story, so you've got time and a reason to play Starcraft and Starcraft: Brood War first.
Warcraft (all of them, well, maybe just II and III)
The Warcraft series is excellent - you should at least play Warcraft III plus its expansion, The Frozen Throne. I played those upon release and only recently went back to play the older games. The first one is a bit frustrating to play due to its primitive control system (click one unit, click move, click where you want it to move to, click the next unit... basically no option to drag select) but if you have the patience, you can get through it. Warcraft II is a huge improvement and highly recommended.
Warhammer 40,000 - Dawn of War (plus all the expansions, plus DoW2)
Yeah, it kind of is just Company of Heroes with a Warhammer 40k theme, but that makes it more of the same, where 'the same' is a good thing, and you can't have too much of a good thing. Also, you're an RTS fan who's played a lot of RTSs and is looking for more, so Dawn of War is a perfect answer.
Supreme Commander (plus Forged Alliance, plus SC2)
You said Total Annihilation was good for the time, well Supreme Commander is Total Annihilation for modern times as its the spiritual successor.
Rise of Legends
You said you loved Rise of Nations, so have you tried this?
Dune series (Dune II, Dune 2000, Emperor - Battle for Dune)
Before Command & Conquer, Westwood Studios made Dune II. They later remade it as Dune 2000 and created a sequel, Emperor, around the time of Red Alert 2. All are worth playing, Emperor especially.
Homeworld (plus Cataclysm and Homeworld 2)
Despite their age, these are excellent space-based RTS. Of course, if you want something along these lines but more recent there's always:
Sins of a Solar Empire (plus Entrenchment and Diplomacy)
An awesome, and incredibly detailed, series of space RTSs. You can get the game bundled with the expansion packs as 'Sins of a Solar Empire: Trinity'.
Star Wars - Empire at War (plus Forces of Corruption)
A Star Wars RTS...
Warhammer - Battle March (plus Mark of Chaos)
An RTS with a classic (medieval) Warhammer style.
Perimeter (plus Emperor's Testament and 2: New Earth)
A RTS that was praised for innovation when it was released, due to its unique terraforming and base defense aspects.
If I think of any more I'll be back...
