The worldgen cookbook threads have plenty of examples, but I'll summarize it with the following:
Parameters that are likely affecting history generation:
World size.If the intent of the world is simply to use a 3x3 embark, there's no need for a 257x257 world. None at all. Pocket worlds (17x17) work in almost all cases.
Number of civs.Again, if the intent of the fortress mode embark is to get sieged, you need a civ count of 2. In 42.06 or 43.03, goblins will come immediately after the population count is reached. By default, once you hit 80 dwarves, you will get sieged. If you change the _SIEGE parameter from 3 to 1, you can get sieges after you hit a population of 20 dwarves.
Embark neighbors.If you make a larger world (this gets worse as the world gets larger) then there's a smaller chance of having the embark neighbors you want. In a pocket world, everyone can reach everyone.
Site Cap after civ creation.I've never seen the value in having this over, say.. somewhere between 0 and 40. Typically, if you need sites at all, which normally you don't, leaving this somewhere between 3 and 10 will work. I have it at zero most of the time.
Population Cap after civ creation.I typically leave this at zero, but 1000-2000 seems to be a reasonable maximum. It doesn't work the way most people think it should work (obviously, given worlds generate just fine with it at zero).
Cull unimportant historical figures.Should always be Yes, no reason i can find for it to ever be No. Who cares if "some guy" did "some thing" in "some region"? You want to know who killed 100 goblins, right?
Reveal all historical events.I typically leave this to yes, but afaik, it only affects what dwarves will engrave or possibly tell stories about, in fortress mode.
Here's a sample world that generates 10,000 years of history in about 10 seconds with very few rejections, and will typically be completely playable in fortress mode, with as many dwarves as you need, caravans, liaisons, kings, all those typical features. And of course, 10,000 iron/steel wearing goblins waiting to attack.
worldgen
[WORLD_GEN]
[TITLE:10K_HISTORY]
[DIM:17:17]
[EMBARK_POINTS:2500]
[END_YEAR:10000]
[BEAST_END_YEAR:10000:-1]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:1]
[ELEVATION:100:400:0:0]
[RAINFALL:0:0:0:0]
[TEMPERATURE:50:75:3200:3200]
[DRAINAGE:0:100:3200:3200]
[VOLCANISM:0:0:0:0]
[SAVAGERY:0:0:0:0]
[ELEVATION_FREQUENCY:2:8:0:0:0:2]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[POLE:NONE]
[MINERAL_SCARCITY:500]
[MEGABEAST_CAP:0]
[SEMIMEGABEAST_CAP:0]
[TITAN_NUMBER:0]
[TITAN_ATTACK_TRIGGER:0:0:0]
[DEMON_NUMBER:6]
[NIGHT_TROLL_NUMBER:0]
[BOGEYMAN_NUMBER:0]
[VAMPIRE_NUMBER:0]
[WEREBEAST_NUMBER:0]
[SECRET_NUMBER:0]
[REGIONAL_INTERACTION_NUMBER:0]
[DISTURBANCE_INTERACTION_NUMBER:0]
[EVIL_CLOUD_NUMBER:0]
[EVIL_RAIN_NUMBER:0]
[GENERATE_DIVINE_MATERIALS:0]
[GOOD_SQ_COUNTS:0:0:0]
[EVIL_SQ_COUNTS:0:0:0]
[PEAK_NUMBER_MIN:0]
[PARTIAL_OCEAN_EDGE_MIN:0]
[COMPLETE_OCEAN_EDGE_MIN:0]
[VOLCANO_MIN:0]
[REGION_COUNTS:SWAMP:0:0:0]
[REGION_COUNTS:DESERT:0:0:0]
[REGION_COUNTS:FOREST:0:0:0]
[REGION_COUNTS:MOUNTAINS:0:0:0]
[REGION_COUNTS:OCEAN:0:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:0:0:0]
[REGION_COUNTS:HILLS:0:0:0]
[EROSION_CYCLE_COUNT:1000]
[RIVER_MINS:0:0]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:0]
[SUBREGION_MAX:5000]
[CAVERN_LAYER_COUNT:1]
[CAVERN_LAYER_OPENNESS_MIN:100]
[CAVERN_LAYER_OPENNESS_MAX:100]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:0]
[CAVERN_LAYER_WATER_MIN:51]
[CAVERN_LAYER_WATER_MAX:52]
[HAVE_BOTTOM_LAYER_1:1]
[HAVE_BOTTOM_LAYER_2:1]
[LEVELS_ABOVE_GROUND:10]
[LEVELS_ABOVE_LAYER_1:21]
[LEVELS_ABOVE_LAYER_2:2]
[LEVELS_ABOVE_LAYER_3:2]
[LEVELS_ABOVE_LAYER_4:2]
[LEVELS_ABOVE_LAYER_5:3]
[LEVELS_AT_BOTTOM:2]
[CAVE_MIN_SIZE:1]
[CAVE_MAX_SIZE:1]
[MOUNTAIN_CAVE_MIN:0]
[NON_MOUNTAIN_CAVE_MIN:0]
[ALL_CAVES_VISIBLE:0]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:2]
[TOTAL_CIV_POPULATION:0]
[SITE_CAP:0]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:0:0:0]
[RAIN_RANGES:0:0:0]
[DRAINAGE_RANGES:0:0:0]
[SAVAGERY_RANGES:0:0:0]
[VOLCANISM_RANGES:0:0:0]