Ah, Atomic Tetris, Starcon (1 and 2), and Scorched Earth. If I ever wanted to hit my siblings really hard, these were good reasons.
I also remember whenever my brother took over the computer, we essentially turned it into a Let's Play session way before they came to existence online. Started off with X-COM. I had my base, he had his. Much fun was had when my skyranger reached a site before his. I lost so much, my base's funding pretty much got cut off, and I was kicked out late-game because I hurt his funding so badly due to not being a good tactician back then. That can also work as a new way to play or LP the game.
I remember learning tons from watching my brothers play games and use other interesting programs (like Fractint (Fractal Generator) and Gravity (planet simulator)). Watching them play Civilization or Master of Orion was generally fun to watch as well. They are, or at least were, outright fearsome to watch. I think the earliest I've seen them beat the game (on at least normal difficulty) was at about 1500 AD, where they overrun cities with Armor tanks and Mechanical Infantries, and bombing the hell out of places with dense airforces. And just to be a dick, finish the last guy's city off with maybe 20 simultaneous ICBMs, or a single militia (or similarly weakest unit available by then), or for the biggest middle finger to the last man standing, a single settler.
If there were any games I played the most solo, it would have to be Stunts, X-COM, Mechwarrior 2: Mercenaries, and Tie Fighter. Beating Tie Fighter at as young as maybe 12 (was it?), freaking awesome. I was pretty much a Top Ace and a pretty decent seat in the Secret Sith Order as well. I mean, I was able to chase down A-Wings and dogfight them with TIE Bombers, I was that good. Minefields became no worry either. And the overall story and music, and everything else involved; screw it, that game rocked.
I still advise using the
D-Fend Reloaded Frontend for DOSBox for anything DOSBox related. Quite user-friendly, easy to tweak things to their best settings, and quick to setup.