Late reply with multiple parts but; Wargame: European Escalation, Wargame: Airland Battle, and Wargame: Red Dragon are all decent choices for single player.

~Wargame: EE has multiple short campaigns each about 5-6 missions long each, completing side-objectives rewards you with command stars which can be used to unlock new units in the campaign and skirmish mode, it's best to unlock only the ones that can be used in the current campaign you're doing. You can reset your command starts for a full refund of them and unlock different units which is useful for starting a different campaign. The campaigns have a perma-death system, if you lose a unit then it is gone for the rest of the campaign unless you chose to restart the mission or revert to an earlier mission or restart the whole campaign for another go. Units are also bloody expensive, and are MORE expensive the higher their veterancy is, and command units are ridiculously expensive, all on top of income being very low so if you lose a command unit you are going to REALLY hurt in not just the current mission, but following missions as well.
Wargame: EE also has a skirmish mode, but you're limited to 5 unit-trees per category, unit-trees being a unit such as the Leopard 1 and it's unlockable variants directly connected to the first line such as the Leopard 1A1->Leopard 1A2->etc. So even if it has 5 units it's all still a part of one "tree", which takes up one slot, leaving you with 4 more unit trees to fill the Tank category for example. So you can pack in the M-60 line, Abrams line, Leclerc line, etc. The decks are still limited to about maybe 25 unit trees, so you still gotta balance between logisitcs, tanks, infantry lines (and their transports, THOSE are also separate unlocks), etc.

~Wargame: Airland Battle is the next game, it does away with unlocking units and instead introduces the more familiar national decks and category system. It's got 4 Risk-style campaigns that need to be completed in an x-amount of days, you have access to strategic points to use for strategic powers like camouflage to hide your unit details, bombing campaigns to affect enemy unit initiative and morale, and more. These same points are also used to call in new battlegroups, which will spawn in whichever destined area they're meant to be in, whether it's an over-land group near the map edges, airborne battlegroups landing at an airfield, marines deploying along coasts, etc. Battles are taken in turns called "days", you send your orders and execute them when you end your turn, if two opposing units meet in a sector they will initiate a real-time battle with no objectives other than reach a set score and minimize your own losses, all under a time limit where whomever has the highest score wins.
Battlegroups have Initiative and Morale, Initiative dictates how many points you can spend in the pre-battle set-up, and Morale dictates how many points-worth of units your opponent needs to destroy in order to win. High Initiative means it'll be easier to get a good head start, and high Morale means you can afford to take more losses before being defeated but you should still strive to avoid losses where possible, as units carry over and the battlegroup may need to Rest on the next turn to replace losses, restore initiative, and raise morale.
Wargame: ALB also introduces fixed-wing (and swing-wing) aircraft as call-in units, these units range from air-superiority fighters to shoot down enemy jets and helicopters, to ground-attack units to wipe out a few to many units, to multi-role craft that do a bit of both, to specialists such as napalm-bombers for anti-garrison work and SEAD craft to snipe enemy anti-air units that have Radar but are otherwise useless against anything else, including AA units that don't have radar.
Wargame: ALB has a skirmish mode and a deck builder a little similar to Wargame: EE, but differs in that decks are built with a single nationality, and may be put under categories which limit unit availability based on a cut-off date (Category A allowing for more recent and advanced units, Category B allowing for some semi-modern units, and Category C being merely okay but still serviceable units) which will affect how many units are available per card. Decks may also be put under more specialized roles such as Armored, Mechanized, Support, Marines, Airborne, and Motorized, all of which will restrict what units you can actually call in but will affect how cheap (or expensive) it will be to put a card into your deck, as well as how many slots will be available for a category. This is sort of seen in Steel Division for example.

Wargame: Red Dragon is the last of the "Wargame" titles, will not talk about WARNO as I do not have that game and thus have no experience on it. While Wargame: ALB featured the introduction to controllable fixed-wing (and swing-wing) aircraft as call-in units, Wargame: RD introduces waterborne craft from modern Destroyers to small riverboats. On top of this, numerous units have been given amphibious capability, so while bridges still provide hotly-contested chokepoints and helicopters still pose some flanking threat if no anti-air is covering the sector, many units can simply cross rivers for a surprise flank attack or divert fire while heavier armor crosses onto those bridges. Additionally, there are dedicated anti-ship units ranging from aircraft to anti-ship rocket artillery, all included in a dedicated Navy section of the deck that can be filled at zero cost, providing a decent addition to every deck for just-in-case one finds themselves on a map that allows Naval units to be called in.

Wargame: RD has a similar risk-style campaign to Wargame: ALB, but does away with strategic abilities and instead has scripted events on set days that affect what battlegroups can be called onto the map. You still have overall objectives to achieve but there are no in-battle objectives, it still plays very similarly to Wargame: ALB on that regard. To also differentiate itself from the previous game, airplanes and airborne units that are embarked are stationed at provinces featuring an airfield, these units can move multiple sectors at a time per turn and provide an extra layer of flexibility, but if their airfield sector is captured they will be lost. Battlegroups The skirmish mode and deck builder is also largely the same, but with a few additions.

The deck builder introduces "coalitions", they function like choosing a nation but allow the full use of said nations units assuming no category or specialization is chosen. However, it is still viable to chose a dedicated single nation as that will provide more units available per card than with a coalition, as well as "prototype" units available only to said nation. You can also chose to do an overall BLUEFOR/REDFOR deck, which gives access to every unit available to one side EXCEPT for prototype units, as well as providing no bonuses to unit availability per card or card cost. There are also DLC nations, some more powerful than others, but they aren't featured in the campaigns at all.

So yeah, all three of these games are decent for singleplayer, I myself have not touched the multiplayer portion and have spent about 1/3rd if not half my playtime just staying in the deck builder putting together various themed decks and comp-stomping when I'm not playing the campaigns.

Originally posted by HistoryPlayer:

Which Wargame title/s is good for Single Player? Im not interested in Multiplayer games

As long as you love time limited missions, first and foremost

The best modern era RTS wargame for single player by far is Regiments by Microprose - blows away all the Eugen titles., It has a feree demo you can try which is massive and provides one of the best campaign maps in the game to play on with several stages to the battle - I played the demo for 15 hrs and then bought the full game it's so good. Far far better than the frantic clickfest that is Wargame/Warno. Just turn the unit speed down to 60% and the damage down to 70% and you have lovely drawn out skirmishes.