Just going back to Warlock again, Steam tells me that I have over 600 hours on Warlock I and over 400 on II. My recommendation for Warlock II though is to add all the DLC, which you can often pick up cheap, and then subscribe to the 'Renaissance' mod. This takes the game to a whole new level, especially if, like me, you play it in sandbox mode with the biggest map and lots of rivals,
One of the aspects where this game shines for me is the sheer number of ways you can beef up your units using purchased equipment or earned perks, so that that even the humblest unit can be made into an elite unit with earned experience. The number of perks is amazing and, even after 400+ of play, I still come accross ones that I had not seen before. Definitely one of my all-time favourite games.
The next closest favourite is Age of Wonders III, although I have played I & II a bit, they are not as good as III. Again, in sandbox mode with the largest possible map and lots of rivals will keep you playing for a long time. Unit improvement is nowhere as near as good as Warlock, but you can do a lot with leaders to equip and improve them, and that is a fun part of the game. Unfortunately though, for units, whilst there is a pretty tame system to beef them up, the game really relies on racing to build the highest 'tier' units, and that makes the lower units a bit redundant, other than s garrison troops.
So here is a way that I have found to be the way to win, so you can take it as a spoiler if you wish.
Build flying units as soon as you can and keep churning 'em out as quick as you can from as many cities as you can and as much as your economy will allow. Also, make sure that you get flying mounts for as many leaders as you can - they are common enough. You can even disband most of the other ships and ground units but do keep a few lower tier units as garrisons to prevent wondering bandits or creatures from walking in. Note that flying units are the fastest and can obviously fly over all terrain types.
Concentrate your flying units in a few very large groups and keep the flow of new units moving to them. By now, with a bit of scouting, you should have identified your next victims cities, and maybe even the faction capitol. There are two ways of doing this; one is to concentrate you your forces against 2-3 cities and then declare war, although you will not ne able to attack until the next turn. If you can provoke the faction to declare war against you, so much the better.
Now, hit them hard with as much as you can amass, but be prepared to taker losses, so make sure you have reserves to hand. If you take 2-3 cities in one or two rounds, chances are that the faction will surrender to you. If your target is the enemy capitol city, then the faction will be defeated.
A tip here is not to include any leaders in the first wave attack as they may well be lost, but keep them back and include them is subsequent waves.
This modus operandi has worked for me every time!